table - Table array with named variables that can contain different types - MATLAB (original) (raw)

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Table array with named variables that can contain different types

Description

table arrays store column-oriented or tabular data, such as columns from a text file or spreadsheet. Tables store each piece of column-oriented data in a variable. Table variables can have different data types and sizes as long as all variables have the same number of rows. Table variables have names, just as the fields of a structure have names. Use thesummary function to get information about a table.

To index into a table, use one of these syntaxes. For more information, see Access Data in Tables.

Dot notation, as in T._`varname`_, extracts one variable.
Curly braces, as inT{_`rows`_,_`vars`_}, extracts an array from specified rows and variables.
Parentheses, as inT(_`rows`_,_`vars`_), returns a table.

You can perform mathematical operations, such as+, .*, and mean, directly on tables. For more information, see Direct Calculations on Tables and Timetables. (since R2023a)

If your data includes timestamps, consider using a timetable instead.

Creation

You can read data from a file into a table using either the Import Tool or the readtable function. Alternatively, use the table function described below to create a table from input data arrays.

You also can create a table that allows space for variables whose values are filled in later. To create a table with preallocated space for variables, use thetable function with 'Size' as the first input argument, as described below.

Syntax

Description

T = table([var1,...,varN](#d126e1781525)) creates a table from the input variables var1,...,varN. The variables can have different sizes and data types, but all variables must have the same number of rows.

If the inputs are workspace variables, then table assigns their names as the variable names in the output table. Otherwise,table assigns variable names of the form'Var1',...,'Var_`N`_', where_`N`_ is the number of variables.

example

T = table('Size',[sz](#d126e1781566),'VariableTypes',[varTypes](#d126e1781601)) creates a table and preallocates space for the variables that have data types you specify. sz is a two-element numeric array, wheresz(1) specifies the number of rows andsz(2) specifies the number of variables.varTypes specifies the data types of the variables.

example

T = table(___,[Name,Value](#namevaluepairarguments)) specifies additional input arguments using one or more name-value pair arguments. For example, you can specify variable names using the'VariableNames' name-value pair. You can use this syntax with any of the input arguments of the previous syntaxes.

example

T = table creates an empty 0-by-0 table.

example

Input Arguments

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`var1,...,varN` — Input variables

arrays

Input variables, specified as arrays with the same number of rows. The input variables can have different sizes and different data types.

Common input variables are numeric arrays, logical arrays, character arrays, structure arrays, or cell arrays. Input variables also can be objects that are arrays. Such an array must support indexing of the formvar(index1,...,indexN), whereindex1 is a numeric or logical vector that corresponds to rows of the variable var. In addition, the array must implement both a vertcat method and asize method with a dim argument.

Example: table([1:4]',ones(4,3,2),eye(4,2)) creates a table from variables with four rows, but different sizes.

Example: table([1:3]',{'one';'two';'three'},categorical({'A';'B';'C'})) creates a table from variables with three rows, but different data types.

`sz` — Size of preallocated table

two-element numeric vector

Size of the preallocated table, specified as a two-element numeric vector. The first element of sz specifies the number of rows, and the second element specifies the number of table variables.

To create variables only, without any rows, specify0 as the first element ofsz.

Example: T = table('Size',[50 3],'VariableTypes',{'string','double','datetime'}) preallocates 50 rows for a table that contains a string array, a double array, and a datetime array.

Example: T = table('Size',[0 4],'VariableTypes',varTypes) specifies zero rows and four variables.

`varTypes` — Data types of preallocated variables

cell array of character vectors | string array

Data types of the preallocated variables, specified as a cell array of character vectors or a string array. The number of types specified by varTypes must equal the number of variables specified by the second element of sz.

varTypes can contain the names of any data types, including the names shown in the table.

Data Type Name	Initial Value in Each Element
'double', 'single'	Double- or single-precision 0
'doublenan','doubleNaN', 'singlenan','singleNaN'	Double- or single-precisionNaN
'int8', 'int16', 'int32', 'int64'	Signed 8-, 16-, 32-, or 64-bit integer 0
'uint8', 'uint16', 'uint32', 'uint64'	Unsigned 8-, 16-, 32-, or 64-bit integer 0
'logical'	0 (false)
'categorical'	categorical value
'datetime'	NaT datetime value
'duration'	0 seconds, as a duration value
'calendarDuration'	0 days, as a calendarDuration value
'string'	(missing string)
'cellstr'	{''} (cell with 0-by-0 character array)
'cell'	{[]} (cell with 0-by-0 double array)
'struct'	Scalar structure with no fields
'table'	Table with no variables
'timetable'	Timetable with no variables and NaT for row times

For any other data type, the initial value is the value used by that type or class to "in-fill" unassigned elements of an array.

If you specify 'char' as a data type, then table preallocates the corresponding variable as a cell array of character vectors, not as a character array. Best practice is to avoid creating table or timetable variables that are character arrays. When working with text data in a table or a timetable, consider using a string array or a categorical array.

Name-Value Arguments

Specify optional pairs of arguments asName1=Value1,...,NameN=ValueN, where Name is the argument name and Value is the corresponding value. Name-value arguments must appear after other arguments, but the order of the pairs does not matter.

Before R2021a, use commas to separate each name and value, and enclose Name in quotes.

Example: T = table(Age,Height,Weight,'RowNames',LastName) creates a table with row names that are specified by the variableLastName.

`VariableNames` — Variable names

cell array of character vectors | string array

Variable names, specified as a cell array of character vectors or a string array whose elements are nonempty and distinct.

The number of names in the array must equal the number of table variables.
The table function also stores the variable names in the VariableNames property of the table.
Variable names can have any Unicode® characters, including spaces and non-ASCII characters.

Example: T = table(lat,lon,'VariableNames',["Latitude","Longitude"]) creates a table from input arrays lat andlon, and names the corresponding table variables Latitude andLongitude.

`RowNames` — Row names

cell array of character vectors | string array

Row names, specified as a cell array of character vectors or a string array whose elements are nonempty and distinct.

The number of names in the array must equal the number of rows.
The table function also stores the row names in the RowNames property of the table.
Row names can have any Unicode characters, including spaces and non-ASCII characters.
The table function removes any leading or trailing whitespace characters from the row names.

Example: T = table(Age,Height,Weight,'RowNames',LastName) creates a table with row names that are specified by the variableLastName.

`DimensionNames` — Dimension names

two-element cell array of character vectors | two-element string array

Since R2021a

Dimension names, specified as a two-element cell array of character vectors or two-element string array whose elements are nonempty and distinct.

The table function also stores the dimension names in the DimensionNames property of the table.
Dimension names can have any Unicode characters, including spaces and non-ASCII characters.

Before R2021a, you can specify dimension names only by setting theDimensionNames property.

Example: T = table(Age,Height,Weight,'RowNames',LastName,'DimensionNames',["PatientName","PatientData"]) creates a table where the name of the first dimension is"PatientName" and the name of the second dimension is "PatientData".

Properties

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Access Table Metadata Properties

A table contains metadata properties that describe the table and its variables. Access these properties using the syntax_`tableName`_.Properties._`PropertyName`_, where _`PropertyName`_ is the name of a property. For example, you can access the names of the variables in tableT using the syntaxT.Properties.VariableNames.

You can return a summary of all the metadata properties using the syntax_`tableName`_.Properties.

Tables provide metadata access through the Properties property because you can access table data directly using dot syntax. For example, if tableT has a variable named Var1, then you can access the values in the variable by using the syntax T.Var1.

Table Metadata

`DimensionNames` — Dimension names

{'Row','Variables'} (default) | two-element cell array of character vectors | two-element string array

Dimension names, specified as a two-element cell array of character vectors or a two-element string array.

Dimension names can have any Unicode characters, including spaces and non-ASCII characters.
If you specify this property using a string array, then it is converted and stored as a cell array of character vectors.

You can access table data using the two dimension names.

If the table has row names, and you use dot syntax and the first dimension name, then you can access the row names as a vector.
If you use dot syntax and the second dimension name, then the data from all the variables are concatenated together in one array, as though you had indexed into the table using{:,:} syntax.

Example

Create a table and display its dimension names. You can access row names and data using dimension names with dot syntax.

load patients T = table(Age,Height,Weight,Systolic,Diastolic, ... 'RowNames',LastName); T.Properties.DimensionNames

ans = 1x2 cell {'Row'} {'Variables'}

Access the row names using the first dimension name. Display the first five names.

ans = 5x1 cell {'Smith' } {'Johnson' } {'Williams'} {'Jones' } {'Brown' }

Access the data using the second dimension name. This syntax is equivalent to T{:,:}.

ans = 100×5

38    71   176   124    93
43    69   163   109    77
38    64   131   125    83
40    67   133   117    75
49    64   119   122    80
46    68   142   121    70
33    64   142   130    88
40    68   180   115    82
28    68   183   115    78
31    66   132   118    86
  ⋮

Modify the names of its dimensions using the Properties.DimensionNames property. Having changed the dimension names, you can access the row names and data using the syntaxes T.Patient and T.Data respectively.

T.Properties.DimensionNames = ["Patient","Data"]; T.Properties

ans = TableProperties with properties:

         Description: ''
            UserData: []
      DimensionNames: {'Patient'  'Data'}
       VariableNames: {'Age'  'Height'  'Weight'  'Systolic'  'Diastolic'}
       VariableTypes: ["double"    "double"    "double"    "double"    "double"]
VariableDescriptions: {}
       VariableUnits: {}
  VariableContinuity: []
            RowNames: {100x1 cell}
    CustomProperties: No custom properties are set.
  Use addprop and rmprop to modify CustomProperties.

`RowNames` — Row names

{} (default) | cell array of character vectors | string array

Row names, specified as a cell array of character vectors or a string array whose elements are nonempty and distinct. IfRowNames is not empty, then the number of row names must equal the number of rows in the table.

Row names can have any Unicode characters, including spaces and non-ASCII characters.
If you assign row names with leading or trailing whitespace characters, then MATLAB® removes them from the row names.
The row names are visible when you view the table. Furthermore, you can use the row names within parentheses or curly braces to access the table data.
Another way to access the row names is to use dot syntax and the name of the first dimension of the table.
If you specify this property using a string array, then it is converted and stored as a cell array of character vectors.

Example

Create a table. Then add row names and access rows by their names.

load patients T = table(Age,Height,Weight,Smoker,Systolic,Diastolic,SelfAssessedHealthStatus); T.SelfAssessedHealthStatus = string(SelfAssessedHealthStatus);

Add row names using the Properties.RowNames property. By default, tables do not have row names, but you can add them at any time.

T.Properties.RowNames = string(LastName); head(T,5)

            Age    Height    Weight    Smoker    Systolic    Diastolic    SelfAssessedHealthStatus
            ___    ______    ______    ______    ________    _________    ________________________

Smith       38       71       176      true        124          93              "Excellent"       
Johnson     43       69       163      false       109          77              "Fair"            
Williams    38       64       131      false       125          83              "Good"            
Jones       40       67       133      false       117          75              "Fair"            
Brown       49       64       119      false       122          80              "Good"

Another way to access the row names is by using dot syntax with the name of the first dimension of the table. Display the first five row names.

T.Properties.DimensionNames

ans = 1x2 cell {'Row'} {'Variables'}

ans = 5x1 cell {'Smith' } {'Johnson' } {'Williams'} {'Jones' } {'Brown' }

Index into the table by row names.

ans=2×7 table Age Height Weight Smoker Systolic Diastolic SelfAssessedHealthStatus ___ ______ ______ ______ ________ _________ ________________________

Smith    38       71       176      true        124          93              "Excellent"       
Brown    49       64       119      false       122          80              "Good"

`Description` — Table description

'' (default) | character vector | string scalar

Table description, specified as a character vector or string scalar. This description is visible when using the summary function.

If you specify this property using a string scalar, then it is converted and stored as a character vector.

Example

Create a table. Modify the description of the table. Display a summary of the result.

load patients T = table(LastName,Age,Height,Weight); T.LastName = string(T.LastName); T.Properties.Description = "Simulated patient data"; summary(T)

T: 100x4 table

Description: Simulated patient data

Variables:

LastName: string
Age: double
Height: double
Weight: double

Statistics for applicable variables:

            NumMissing      Min         Median         Max         Mean            Std    

LastName        0                                                                         
Age             0            25              39         50        38.2800         7.2154  
Height          0            60              67         72        67.0700         2.8365  
Weight          0           111        142.5000        202            154        26.5714

`UserData` — Additional table information

[] (default) | array

Additional table information, specified as an array. You can attach data of any kind to a table using this property.

Example

Create a table. Attach an anonymous function as a piece of user data that is associated with the table.

load patients T = table(LastName,Age,Height,Weight,Smoker,Systolic,Diastolic); formula = @(x) x.^2; T.Properties.UserData = formula; T.Properties

ans = TableProperties with properties:

         Description: ''
            UserData: @(x)x.^2
      DimensionNames: {'Row'  'Variables'}
       VariableNames: {'LastName'  'Age'  'Height'  'Weight'  'Smoker'  'Systolic'  'Diastolic'}
       VariableTypes: ["cell"    "double"    "double"    "double"    "logical"    "double"    "double"]
VariableDescriptions: {}
       VariableUnits: {}
  VariableContinuity: []
            RowNames: {}
    CustomProperties: No custom properties are set.
  Use addprop and rmprop to modify CustomProperties.

Variable Metadata

`VariableNames` — Variable names

cell array of character vectors | string array

Variable names, specified as a cell array of character vectors or a string array whose elements are nonempty and distinct. The number of names must equal the number of variables.

Variable names can have any Unicode characters, including spaces and non-ASCII characters.
The variable names are visible when viewing the table and when using the summary function. Furthermore, you can use the variable names within parentheses, within curly braces, or with dot indexing to access table data.
If you specify this property using a string array, then it is converted and stored as a cell array of character vectors.

Example

Create a table with default variable names. Then modify the names using the Properties.VariableNames property.

T = table(["Smith";"Nguyen";"Williams";"Fernandez";"Brown"],[38;43;38;40;49], ... [71;69;64;67;64],[176;163;131;133;119])

T=5×4 table Var1 Var2 Var3 Var4 ___________ ____ ____ ____

"Smith"         38      71     176 
"Nguyen"        43      69     163 
"Williams"      38      64     131 
"Fernandez"     40      67     133 
"Brown"         49      64     119

T.Properties.VariableNames = ["LastName","Age","Height","Weight"]

T=5×4 table LastName Age Height Weight ___________ ___ ______ ______

"Smith"        38       71       176  
"Nguyen"       43       69       163  
"Williams"     38       64       131  
"Fernandez"    40       67       133  
"Brown"        49       64       119

A fundamental way to display and modify variables is to access them by name using dot syntax.

T=5×4 table LastName Age Height Weight ___________ ___ ______ ______

"Smith"        53       71       176  
"Nguyen"       43       69       163  
"Williams"     38       64       131  
"Fernandez"    40       67       133  
"Brown"        49       64       119

`VariableTypes` — Variable data types

string array | cell array of character vectors

Since R2024b

Variable data types, specified as a string array or a cell array of character vectors.

Example

Create a table.

load patients T = table(LastName,Age,Height,Weight,Smoker,SelfAssessedHealthStatus)

T=100×6 table LastName Age Height Weight Smoker SelfAssessedHealthStatus ____________ ___ ______ ______ ______ ________________________

{'Smith'   }    38       71       176      true           {'Excellent'}      
{'Johnson' }    43       69       163      false          {'Fair'     }      
{'Williams'}    38       64       131      false          {'Good'     }      
{'Jones'   }    40       67       133      false          {'Fair'     }      
{'Brown'   }    49       64       119      false          {'Good'     }      
{'Davis'   }    46       68       142      false          {'Good'     }      
{'Miller'  }    33       64       142      true           {'Good'     }      
{'Wilson'  }    40       68       180      false          {'Good'     }      
{'Moore'   }    28       68       183      false          {'Excellent'}      
{'Taylor'  }    31       66       132      false          {'Excellent'}      
{'Anderson'}    45       68       128      false          {'Excellent'}      
{'Thomas'  }    42       66       137      false          {'Poor'     }      
{'Jackson' }    25       71       174      false          {'Poor'     }      
{'White'   }    39       72       202      true           {'Excellent'}      
{'Harris'  }    36       65       129      false          {'Good'     }      
{'Martin'  }    48       71       181      true           {'Good'     }      
  ⋮

Display the data types of the table variables.

T.Properties.VariableTypes

ans = 1x6 string "cell" "double" "double" "double" "logical" "cell"

You can also use the property to convert table variables to other data types. For example, convert the first variable to a string array and the last variable to a categorical array.

T.Properties.VariableTypes = ["string" "double" "double" "double" "logical" "categorical"]

T=100×6 table LastName Age Height Weight Smoker SelfAssessedHealthStatus __________ ___ ______ ______ ______ ________________________

"Smith"       38       71       176      true             Excellent        
"Johnson"     43       69       163      false            Fair             
"Williams"    38       64       131      false            Good             
"Jones"       40       67       133      false            Fair             
"Brown"       49       64       119      false            Good             
"Davis"       46       68       142      false            Good             
"Miller"      33       64       142      true             Good             
"Wilson"      40       68       180      false            Good             
"Moore"       28       68       183      false            Excellent        
"Taylor"      31       66       132      false            Excellent        
"Anderson"    45       68       128      false            Excellent        
"Thomas"      42       66       137      false            Poor             
"Jackson"     25       71       174      false            Poor             
"White"       39       72       202      true             Excellent        
"Harris"      36       65       129      false            Good             
"Martin"      48       71       181      true             Good             
  ⋮

`VariableDescriptions` — Variable descriptions

{} (default) | cell array of character vectors | string array

Variable descriptions, specified as a cell array of character vectors or a string array This property can be an empty cell array, which is the default. If the array is not empty, then it must contain as many elements as there are variables. You can specify an individual empty character vector or empty string for a variable that does not have a description.

The variable descriptions are visible when using thesummary function.
If you specify this property using a string array, then it is converted and stored as a cell array of character vectors.

Example

Create a table. Modify the variable descriptions. Display a summary of the result.

load patients T = table(LastName,Age,Height,Weight,Smoker,Systolic,Diastolic); T.LastName = string(T.LastName); T.Properties.VariableDescriptions = ["","","","", ... "Has the patient ever been a smoker", ... "Systolic Pressure","Diastolic Pressure"]; summary(T)

T: 100x7 table

Variables:

LastName: string
Age: double
Height: double
Weight: double
Smoker: logical (34 true, Has the patient ever been a smoker)
Systolic: double (Systolic Pressure)
Diastolic: double (Diastolic Pressure)

Statistics for applicable variables:

             NumMissing      Min         Median         Max          Mean            Std    

LastName         0                                                                          
Age              0            25              39         50         38.2800         7.2154  
Height           0            60              67         72         67.0700         2.8365  
Weight           0           111        142.5000        202             154        26.5714  
Systolic         0           109             122        138        122.7800         6.7128  
Diastolic        0            68         81.5000         99         82.9600         6.9325

`VariableUnits` — Variable units

{} (default) | cell array of character vectors | string array

Variable units, specified as a cell array of character vectors or a string array. This property can be an empty cell array, which is the default. If the array is not empty, then it must contain as many elements as there are variables. You can specify an individual empty character vector or empty string for a variable that does not have units.

The variable units are visible when using thesummary function.
If you specify this property using a string array, then it is converted and stored as a cell array of character vectors.

Example

Create a table. Modify the variable units. Display a summary of the result.

load patients T = table(LastName,Age,Height,Weight,Smoker,Systolic,Diastolic); T.LastName = string(T.LastName); T.Properties.VariableUnits = ["","Yrs","In","Lbs","","mm Hg","mm Hg"]; summary(T)

T: 100x7 table

Variables:

LastName: string
Age: double (Yrs)
Height: double (In)
Weight: double (Lbs)
Smoker: logical (34 true)
Systolic: double (mm Hg)
Diastolic: double (mm Hg)

Statistics for applicable variables:

             NumMissing      Min         Median         Max          Mean            Std    

LastName         0                                                                          
Age              0            25              39         50         38.2800         7.2154  
Height           0            60              67         72         67.0700         2.8365  
Weight           0           111        142.5000        202             154        26.5714  
Systolic         0           109             122        138        122.7800         6.7128  
Diastolic        0            68         81.5000         99         82.9600         6.9325

`VariableContinuity` — Status as continuous or discrete variables

[] (default) | cell array of character vectors | string array

Status as continuous or discrete variables, specified as a cell array of character vectors or a string array.

While tables and timetables both have this property, only timetables use it. For more information, see theVariableContinuity property of timetable.

Custom Metadata

`CustomProperties` — Customized metadata of table and its variables

CustomProperties object

Customized metadata of a table and its variables, specified as aCustomProperties object.

The CustomProperties object is a container for customized metadata that you can add to a table. By default,CustomProperties has zero properties. Each property you add to CustomProperties can contain either table metadata or variable metadata. If a property contains variable metadata, then its value must be an array, and the number of elements in the array must equal the number of table variables.

To add properties for customized metadata to a table, use theaddprop function.
To access or modify customized metadata, use the syntax_`tableName`_.Properties.CustomProperties._`PropertyName`_. In this syntax,_`PropertyName`_ is the name you chose when you added that property usingaddprop.
To remove properties, use the rmprop function.

Note: You can add or remove only properties for customized metadata usingaddprop and rmprop. You cannot add or remove properties of the_`tableName`_.Properties object.

Example

Create a table.

load patients T = table(LastName,Age,Height,Weight,Smoker,Systolic,Diastolic);

Add properties that can hold customized metadata about the table and its variables. In this example, the metadata are names of instruments, true and false values indicating whether variables are to be plotted, and the name of an output file. To add properties, use the addprop function.

T = addprop(T,["Instrument","ToPlot","OutputFile"],["variable","variable","table"]); T.Properties

ans = TableProperties with properties:

         Description: ''
            UserData: []
      DimensionNames: {'Row'  'Variables'}
       VariableNames: {'LastName'  'Age'  'Height'  'Weight'  'Smoker'  'Systolic'  'Diastolic'}
       VariableTypes: ["cell"    "double"    "double"    "double"    "logical"    "double"    "double"]
VariableDescriptions: {}
       VariableUnits: {}
  VariableContinuity: []
            RowNames: {}

Custom Properties (access using t.Properties.CustomProperties.): OutputFile: [] Instrument: [] ToPlot: []

Assign values to the customized metadata using dot syntax. When you assign an array of text values to customized metadata, the best practice is to use a string array, not a cell array of character vectors. If a property of CustomProperties is a cell array of character vectors, then there is no mechanism to prevent you from later assigning nontext values as elements of the cell array.

T.Properties.CustomProperties.Instrument = ["","","height rod","scale","","blood pressure cuff","blood pressure cuff"]; T.Properties.CustomProperties.ToPlot = [false false true true false true true]; T.Properties.CustomProperties.OutputFile = 'patientData.csv'; T.Properties

ans = TableProperties with properties:

         Description: ''
            UserData: []
      DimensionNames: {'Row'  'Variables'}
       VariableNames: {'LastName'  'Age'  'Height'  'Weight'  'Smoker'  'Systolic'  'Diastolic'}
       VariableTypes: ["cell"    "double"    "double"    "double"    "logical"    "double"    "double"]
VariableDescriptions: {}
       VariableUnits: {}
  VariableContinuity: []
            RowNames: {}

Custom Properties (access using t.Properties.CustomProperties.): OutputFile: 'patientData.csv' Instrument: ["" "" "height rod" "scale" "" "blood pressure cuff" "blood pressure cuff"] ToPlot: [0 0 1 1 0 1 1]

Remove the OutputFile property from T.

T = rmprop(T,"OutputFile"); T.Properties

ans = TableProperties with properties:

         Description: ''
            UserData: []
      DimensionNames: {'Row'  'Variables'}
       VariableNames: {'LastName'  'Age'  'Height'  'Weight'  'Smoker'  'Systolic'  'Diastolic'}
       VariableTypes: ["cell"    "double"    "double"    "double"    "logical"    "double"    "double"]
VariableDescriptions: {}
       VariableUnits: {}
  VariableContinuity: []
            RowNames: {}

Custom Properties (access using t.Properties.CustomProperties.): Instrument: ["" "" "height rod" "scale" "" "blood pressure cuff" "blood pressure cuff"] ToPlot: [0 0 1 1 0 1 1]

Examples

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Store data about a group of patients in a table. You can perform calculations and store results in the same table. Also, you can annotate the table to describe your work and the variables of the table.

First, create workspace variables that have the patient data. The variables can have any data types but must have the same number of rows.

LastName = {'Sanchez';'Johnson';'Li';'Diaz';'Brown'}; Age = [38;43;38;40;49]; Smoker = logical([1;0;1;0;1]); Height = [71;69;64;67;64]; Weight = [176;163;131;133;119]; BloodPressure = [124 93; 109 77; 125 83; 117 75; 122 80];

Create a table, T, as a container for the workspace variables. The table function uses the workspace variable names as the names of the table variables in T. A table variable can have multiple columns. For example, the BloodPressure variable in T is a 5-by-2 array.

T = table(LastName,Age,Smoker,Height,Weight,BloodPressure)

T=5×6 table LastName Age Smoker Height Weight BloodPressure ___________ ___ ______ ______ ______ _____________

{'Sanchez'}    38     true        71       176       124     93  
{'Johnson'}    43     false       69       163       109     77  
{'Li'     }    38     true        64       131       125     83  
{'Diaz'   }    40     false       67       133       117     75  
{'Brown'  }    49     true        64       119       122     80

You can use dot indexing to access table variables. For example, calculate the mean height of the patients using the values in T.Height.

meanHeight = mean(T.Height)

Calculate body mass index (BMI), and add it as a new table variable. You also can add and name table variables in one step, using dot syntax.

T.BMI = (T.Weight0.453592)./(T.Height0.0254).^2

T=5×7 table LastName Age Smoker Height Weight BloodPressure BMI
___________ ___ ______ ______ ______ _____________ ______

{'Sanchez'}    38     true        71       176       124     93      24.547
{'Johnson'}    43     false       69       163       109     77      24.071
{'Li'     }    38     true        64       131       125     83      22.486
{'Diaz'   }    40     false       67       133       117     75      20.831
{'Brown'  }    49     true        64       119       122     80      20.426

Annotate the table with a description of the BMI calculation. You can annotate T and its variables using metadata accessed through T.Properties.

T.Properties.Description = 'Patient data, including body mass index (BMI) calculated using Height and Weight'; T.Properties

ans = TableProperties with properties:

         Description: 'Patient data, including body mass index (BMI) calculated using Height and Weight'
            UserData: []
      DimensionNames: {'Row'  'Variables'}
       VariableNames: {'LastName'  'Age'  'Smoker'  'Height'  'Weight'  'BloodPressure'  'BMI'}
       VariableTypes: ["cell"    "double"    "logical"    "double"    "double"    "double"    "double"]
VariableDescriptions: {}
       VariableUnits: {}
  VariableContinuity: []
            RowNames: {}
    CustomProperties: No custom properties are set.
  Use addprop and rmprop to modify CustomProperties.

Access All Table Data as Matrix

Access all the data from a table as a matrix, using the name of the second dimension of the table.

Create a table that has five rows of data about a set of patients.

Age = [38;43;38;40;49]; Smoker = logical([1;0;1;0;1]); Height = [71;69;64;67;64]; Weight = [176;163;131;133;119]; BloodPressure = [124 93; 109 77; 125 83; 117 75; 122 80];

T = table(Age,Smoker,Height,Weight,BloodPressure)

T=5×5 table Age Smoker Height Weight BloodPressure ___ ______ ______ ______ _____________

38     true        71       176       124     93  
43     false       69       163       109     77  
38     true        64       131       125     83  
40     false       67       133       117     75  
49     true        64       119       122     80

Display the names of the table dimensions using the DimensionNames property. The default name of the second dimension is Variables.

T.Properties.DimensionNames

ans = 1x2 cell {'Row'} {'Variables'}

Access the table data as a matrix using the syntax T.Variables. This syntax is equivalent to accessing all the contents using curly brace syntax, T{:,:}. If the table data cannot be concatenated into a matrix, then an error message is raised.

ans = 5×6

38     1    71   176   124    93
43     0    69   163   109    77
38     1    64   131   125    83
40     0    67   133   117    75
49     1    64   119   122    80

Rename the second dimension. If you change the name, then you can use the new name to access the data.

T.Properties.DimensionNames{2} = 'PatientData'; T.PatientData

ans = 5×6

38     1    71   176   124    93
43     0    69   163   109    77
38     1    64   131   125    83
40     0    67   133   117    75
49     1    64   119   122    80

Specify Size and Variable Types

Preallocate a table by specifying its size and the data types of the variables. The table function fills the variables with default values that are appropriate for the data types you specify. It also gives the variables default names, but you also can assign variable names of your own. Preallocation provides room for data you add to the table later.

sz = [4 3]; varTypes = {'double','datetime','string'}; T = table('Size',sz,'VariableTypes',varTypes)

T=4×3 table Var1 Var2 Var3
____ ____ _________

 0      NaT     <missing>
 0      NaT     <missing>
 0      NaT     <missing>
 0      NaT     <missing>

To specify names for the variables, use the 'VariableNames' name-value pair argument.

varNames = {'Temperature','Time','Station'}; T2 = table('Size',sz,'VariableTypes',varTypes,'VariableNames',varNames)

T2=4×3 table Temperature Time Station ___________ ____ _________

     0         NaT     <missing>
     0         NaT     <missing>
     0         NaT     <missing>
     0         NaT     <missing>

Add rows of data to the first two rows of T2. Preallocation can be a useful technique when your code adds one row of data, or a few rows of data, at a time. Instead of growing the table every time you add a row, you can fill in table variables that already have room for your data.

T2(1,:) = {75,datetime('now'),"S1"}; T2(2,:) = {68,datetime('now')+1,"S2"}

T2=4×3 table Temperature Time Station ___________ ____________________ _________

    75         23-Jan-2025 00:30:22    "S1"     
    68         24-Jan-2025 00:30:22    "S2"     
     0                          NaT    <missing>
     0                          NaT    <missing>

You can encapsulate a row of data values in a cell array. When you assign a row from a cell array, elements from the cell array are assigned to the row in the table.

Specify Variable Names

Create a table from arrays. To specify table variable names, use the 'VariableNames' name-value pair argument. For example, you can use 'VariableNames' to specify names when the other input arguments are not workspace variables.

T = table(categorical({'M';'F';'M'}),[45;32;34],... {'NY';'CA';'MA'},logical([1;0;0]),... 'VariableNames',{'Gender','Age','State','Vote'})

T=3×4 table Gender Age State Vote ______ ___ ______ _____

  M       45     {'NY'}    true 
  F       32     {'CA'}    false
  M       34     {'MA'}    false

Create a table with the state names as row names. You can specify both the 'VariableNames' and 'RowNames' name-value pairs when using the table function.

T = table(categorical({'M';'F';'M'}),[45;32;34],logical([1;0;0]),... 'VariableNames',{'Gender','Age','Vote'},... 'RowNames',{'NY';'CA';'MA'})

T=3×3 table Gender Age Vote ______ ___ _____

NY      M       45     true 
CA      F       32     false
MA      M       34     false

Specify Row Names

Specify row names for a table. Tables do not have to have row names, but if you specify them, then you can index into a table by row name. You also can access the set of row names using the name of the first dimension of a table.

Create arrays containing patient data.

LastName = {'Sanchez';'Johnson';'Lee';'Diaz';'Brown'}; Age = [38;43;38;40;49]; Height = [71;69;64;67;64]; Weight = [176;163;131;133;119];

Create a table containing the arrays. Specify LastName as the source of row names for the table. The table has only three variables. The row names are not a table variable, but instead a property of the table.

T = table(Age,Weight,Height,'RowNames',LastName)

T=5×3 table Age Weight Height ___ ______ ______

Sanchez    38      176        71  
Johnson    43      163        69  
Lee        38      131        64  
Diaz       40      133        67  
Brown      49      119        64

Since the rows have row names, you can index into the rows of T by name.

ans=1×3 table Age Weight Height ___ ______ ______

Lee    38      131        64

To specify multiple rows, use a cell array.

ans=2×3 table Age Weight Height ___ ______ ______

Lee      38      131        64  
Brown    49      119        64

To access all the row names of T as a cell array, use the syntax T.Row. By default, Row is the name of the first dimension of a table.

ans = 5x1 cell {'Sanchez'} {'Johnson'} {'Lee' } {'Diaz' } {'Brown' }

Change the name of the first dimension. If you change the name, then you can access the row names using the new name.

T.Properties.DimensionNames{1} = 'LastNames'; T.LastNames

ans = 5x1 cell {'Sanchez'} {'Johnson'} {'Lee' } {'Diaz' } {'Brown' }

Specify Table Variables and Row Names Using String Arrays

Starting in R2017a, you can create strings using double quotes, and add string arrays as table variables.

FlightNum = [1261;547;3489]; Customer = ["Jones";"Brown";"Smith"]; Date = datetime(2016,12,20:22)'; Rating = categorical(["Good";"Poor";"Fair"]); Comment = ["Flight left on time, not crowded";... "Late departure, ran out of dinner options";... "Late, but only by half an hour. Otherwise fine."]; T = table(FlightNum,Customer,Date,Rating,Comment)

T=3×5 table FlightNum Customer Date Rating Comment
_________ ________ ___________ ______ _________________________________________________

  1261       "Jones"     20-Dec-2016     Good     "Flight left on time, not crowded"               
   547       "Brown"     21-Dec-2016     Poor     "Late departure, ran out of dinner options"      
  3489       "Smith"     22-Dec-2016     Fair     "Late, but only by half an hour. Otherwise fine."

To use the text in a string array as row names, convert the string array to a cell array of character vectors. Then create a table with row names.

Customer = cellstr(Customer); T = table(FlightNum,Date,Rating,Comment,'RowNames',Customer)

T=3×4 table FlightNum Date Rating Comment
_________ ___________ ______ _________________________________________________

Jones      1261       20-Dec-2016     Good     "Flight left on time, not crowded"               
Brown       547       21-Dec-2016     Poor     "Late departure, ran out of dinner options"      
Smith      3489       22-Dec-2016     Fair     "Late, but only by half an hour. Otherwise fine."

Build Table by Assigning Variables Individually

Create workspace variables containing snowfall totals on different dates at three locations. These variables are row vectors.

Date = {'12/25/11','1/2/12','1/23/12','2/7/12','2/15/12'}; location1 = [20 5 13 0 17]; location2 = [18 9 21 5 12]; location3 = [26 10 16 3 15];

One way to create a table from these variables is to call the table function with the syntax T = table(Date',location1',location2',location3'). Because the workspace variables are row vectors, you must transpose them to put them into the table as column-oriented data. Therefore, the input arguments are expressions, not simple variables. As a result, table creates T with the default variable names Var1, Var2, Var3, and Var4. You can assign more meaningful names to T.Properties.VariableNames after you create T. But, it might be more convenient to create an empty table, and then add variables one at a time with new names.

Create an empty table. Transpose the workspace variables and add them to the table as column vectors. As part of assigning each workspace variable into T, provide a meaningful name for the table variable.

T = table; T.Date = Date'; T.Natick = location1'; T.Boston = location2'; T.Worcester = location3'

T=5×4 table Date Natick Boston Worcester ____________ ______ ______ _________

{'12/25/11'}      20        18         26    
{'1/2/12'  }       5         9         10    
{'1/23/12' }      13        21         16    
{'2/7/12'  }       0         5          3    
{'2/15/12' }      17        12         15

Specify Variable Names Using Any Characters

Starting in R2019b, you can specify table variable names that are not valid MATLAB® identifiers. Such variable names can include spaces, non-ASCII characters, and can have any character as the leading character. When you access such a variable name, enclose it quotation marks.

Create a table that stores data about a set of patients. Start with their ages and status as smokers.

Age = [38;43;38;40;49]; Smoker = logical([1;0;1;0;1]); Height = [71;69;64;67;64]; Weight = [176;163;131;133;119]; BloodPressure = [124 93; 109 77; 125 83; 117 75; 122 80]; T = table(Age,Smoker)

T=5×2 table Age Smoker ___ ______

38     true  
43     false 
38     true  
40     false 
49     true

Add the blood pressure readings with the variable name '29-May-2019 Blood Pressure Reading'. You can use dot syntax to add or access the variable. Since its name is not a valid MATLAB identifier, use parentheses and quotation marks with dot syntax.

T.('29-May-2019 Blood Pressure Reading') = BloodPressure

T=5×3 table Age Smoker 29-May-2019 Blood Pressure Reading ___ ______ __________________________________

38     true                  124     93            
43     false                 109     77            
38     true                  125     83            
40     false                 117     75            
49     true                  122     80

When table variable names are valid MATLAB identifiers, you can use dot syntax without parentheses and quotation marks.

T.Height = Height; T.Weight = Weight

T=5×5 table Age Smoker 29-May-2019 Blood Pressure Reading Height Weight ___ ______ __________________________________ ______ ______

38     true                  124     93                  71       176  
43     false                 109     77                  69       163  
38     true                  125     83                  64       131  
40     false                 117     75                  67       133  
49     true                  122     80                  64       119

Index into T using variable names.

T(:,{'Age','Smoker','29-May-2019 Blood Pressure Reading'})

ans=5×3 table Age Smoker 29-May-2019 Blood Pressure Reading ___ ______ __________________________________

38     true                  124     93            
43     false                 109     77            
38     true                  125     83            
40     false                 117     75            
49     true                  122     80

Limitations

Use single quotes for these input names:
- 'DimensionNames' (since R2021a)
- 'RowNames'
- 'Size'
- 'VariableTypes'
- 'VariableNames'
  To avoid confusion with variable inputs, do not use double-quoted string scalars (such as "RowNames") for these names.

Tips

For a list of functions that accept or return tables, see Tables.

Extended Capabilities

Tall Arrays

Calculate with arrays that have more rows than fit in memory.

Thetable function supports tall arrays with the following usage notes and limitations:

The syntax TT = table(T1,T2,...) constructs a tall table from several tall arrays (T1,T2,...). You can use the VariableNames name-value argument to specify variable names.
The VariableTypes property is not supported.

For more information, see Tall Arrays.

C/C++ Code Generation

Generate C and C++ code using MATLAB® Coder™.

Usage notes and limitations:

Starting in R2019b, you can use tables in MATLAB code intended for code generation. For more information, seeCode Generation for Tables (MATLAB Coder) andTable Limitations for Code Generation (MATLAB Coder).

Thread-Based Environment

Run code in the background using MATLAB® backgroundPool or accelerate code with Parallel Computing Toolbox™ ThreadPool.

Distributed Arrays

Partition large arrays across the combined memory of your cluster using Parallel Computing Toolbox™.

Usage notes and limitations:

The input arrays must be distributed and have the same number of rows.
The result is distributed, using a 1D distribution scheme over the first dimension.

For more information, see Run MATLAB Functions with Distributed Arrays (Parallel Computing Toolbox).

Version History

Introduced in R2013b

expand all

R2024b: `VariableTypes` property of tables and timetables specifies the data types of their variables

The VariableTypes property of tables and timetables specifies the data types of their variables.

R2023a: Perform calculations directly on tables and timetables without extracting their data

You can now perform calculations directly on tables and timetables without extracting their data. All the variables in your tables and timetables must have data types that support calculations. You can also perform operations where one operand is a table or timetable and the other is a numeric or logical array. Previously, all calculations required you to extract data from your tables and timetables by indexing into them.

For more information, see Direct Calculations on Tables and Timetables and Rules for Table and Timetable Mathematics.

R2022a: Improved performance when subscripting with dot notation or multiple levels of indexing

Subscripting when using dot notation is significantly faster in R2022a than in R2021b. Also, subscripting with multiple levels of indexing is faster.

For example, when you use dot notation to refer to a table variable with 106 elements, performance in R2022a is more than 4x faster than in R2021b.
function timingTest()
t = table(zeros(1e6,1), ones(1e6,1), nan(1e6,1));
indices = 1:10000;

tic;
% Refer to variable using dot notation
for i = indices
x = t.Var1;
end
toc

end
The approximate execution times are:
R2021b: 0.15 s
R2022a: 0.035 s

Similarly, when you use dot notation to assign an array to a table variable with 106 elements, performance in R2022a is about 3.6x faster than in R2021b.
function timingTest()
t = table(zeros(1e6,1), ones(1e6,1), nan(1e6,1));
indices = 1:10000;
x = randi(1e6,1e6,1);
tic;
% Assign to variable using dot notation
for i = indices
t.Var1 = x;
end
toc
end
The approximate execution times are:
R2021b: 0.23 s
R2022a: 0.063 s
Also, when you use dot notation and parentheses to assign individual values to elements of a table variable, performance in R2022a is more than 4x faster than in R2021b.
function timingTest()
t = table(zeros(1e6,1), ones(1e6,1), nan(1e6,1));
indices = randi(1e6,1,10000);
tic;
% Assign to elements using dot notation and parentheses
for i = indices
t.Var1(i) = rand;
end
toc
end
The approximate execution times are:
R2021b: 0.53 s
R2022a: 0.12 s

The code was timed on a Windows® 10, Intel® Xeon CPU W-2133 @ 3.60 GHz test system by calling each version of thetimingTest function.

R2021b: Improved performance when assigning elements by subscripting with curly braces

Subscripted assignment using curly braces is significantly faster in R2021b than in R2021a.

For example, when you assign into three table variables with 106 elements, performance in R2021b is approximately 4.4x faster, as shown below.

function timingTest() t = table(zeros(1e6,1), ones(1e6,1), nan(1e6,1)); indices = randi(1e6,1,10000);

tic;
% Assign row vector of random values to randomly chosen row
for i = indices
    t{i,:} = rand(1,3);
end
toc

end

The approximate execution times are:

R2021a: 7.4 s

R2021b: 1.7 s

The code was timed on a Windows 10 system with a 3.6 GHz Intel Xeon W-2133 CPU by calling the timingTest function in R2021a and R2021b.

R2021a: Dimension names cannot match reserved names

MATLAB raises an error if you assign a dimension name that matches one of these reserved names: 'Properties','RowNames', 'VariableNames', or':'. In previous releases, MATLAB raised a warning and modified the dimension names so that they were different from the reserved names.

R2020a: Improved performance when assigning elements by subscripting into table variables

Subscripted assignment into table variables is significantly faster. Performance is essentially constant with the number of elements in each table variable.

For example, when you use dot indexing to assign elements to a variable with 106 elements, performance in R2020a is approximately 2x faster than in R2019b, as shown below.
function timingTest()
t = table(zeros(1e6,1));
indices = randi(1e6,1,10000);
tic;
for i = indices
t.Var1(i) = rand;
end
toc
end
The approximate execution times are:
R2019b: 1.20 s
R2020a: 0.59 s
Similarly, assignment using curly braces is faster. When you assign into three table variables with 106 elements, performance in R2020a is approximately 1.2x faster than in R2019b, as shown below.
function timingTest()
t = table(zeros(1e6,1), ones(1e6,1), nan(1e6,1));
indices = randi(1e6,1,10000);
tic;
for i = indices
t{i,:} = rand;
end
toc
end
The approximate execution times are:
R2019b: 8.04 s
R2020a: 6.68 s

The code was timed on a Windows 10, Intel Xeon® W-2133 @ 3.60 GHz test system by calling the functiontimingTest.

The performance improvement occurs only when you make table subscripted assignments within a function. There is no improvement when subscripting into tables at the command line, or within try-catch blocks.

R2019b: Variable names can contain leading and trailing whitespace characters

Table and timetable variable names with leading or trailing whitespace characters are not modified.

In previous releases, leading and trailing whitespace characters were deleted from variable names when you specified them using the 'VariableNames' name-value pair argument, or assigned them to the VariableNames property.

To manually remove such characters, first use the strtrim function on the names, then assign them as variable names to the table or timetable.

R2019b: Variable names and dimension names must be unique

MATLAB raises an error if you assign a table variable name that matches a dimension name, or a dimension name that matches a variable name. In previous releases, MATLAB raised a warning and modified the names so they were unique.

R2019b: Improved performance when assigning elements by subscripting into large table variables

Subscripted assignment into large table variables is significantly faster. Performance is now essentially constant with the number of elements in each table variable.

For example, when you use dot indexing to assign elements to a variable with 106 elements, performance in R2019b is approximately 40x times faster, as shown below.
function timingTest()
t = table(zeros(1e6,1));
indices = randi(1e6,1,10000);
tic;
for i = indices
t.Var1(i) = rand;
end
toc
end
The approximate execution times are:
R2019a: 47.83 s
R2019b: 1.20 s
Similarly, assignment using curly braces is faster. For example, when you assign into three table variables with 106 elements, performance in R2019b is approximately 18x faster.
function timingTest()
t = table(zeros(1e6,1), ones(1e6,1), nan(1e6,1));
indices = randi(1e6,1,10000);
tic;
for i = indices
t{i,:} = rand;
end
toc
end
The approximate execution times are:
R2019a: 156.39 s
R2019b: 8.51 s

The code was timed on a Windows 10 system with a 3.6 GHz Intel Xeon W-2133 CPU by calling each version of thetimingTest function.

The larger the table variables are, the greater the performance improvement becomes. However, the performance improvement occurs only when you make table subscripted assignments within a function. There is no improvement when subscripting into tables at the command line, or within try-catch blocks.

table - Table array with named variables that can contain different types - MATLAB (original) (raw)

Description

Creation

Syntax

Description

Input Arguments

var1,...,varN — Input variables

sz — Size of preallocated table

varTypes — Data types of preallocated variables

VariableNames — Variable names

RowNames — Row names

DimensionNames — Dimension names

Properties

Table Metadata

DimensionNames — Dimension names

Example

RowNames — Row names

Example

Description — Table description

Example

UserData — Additional table information

Example

Variable Metadata

VariableNames — Variable names

Example

VariableTypes — Variable data types

Example

VariableDescriptions — Variable descriptions

Example

VariableUnits — Variable units

Example

VariableContinuity — Status as continuous or discrete variables

Custom Metadata

CustomProperties — Customized metadata of table and its variables

Example

Examples

Store Related Data Variables in Table

Access All Table Data as Matrix

Specify Size and Variable Types

Specify Variable Names

Specify Row Names

Specify Table Variables and Row Names Using String Arrays

Build Table by Assigning Variables Individually

Specify Variable Names Using Any Characters

Limitations

Tips

Extended Capabilities

Tall Arrays

C/C++ Code Generation

Thread-Based Environment

Distributed Arrays

Version History

R2024b: VariableTypes property of tables and timetables specifies the data types of their variables

R2023a: Perform calculations directly on tables and timetables without extracting their data

R2022a: Improved performance when subscripting with dot notation or multiple levels of indexing

R2021b: Improved performance when assigning elements by subscripting with curly braces

R2021a: Dimension names cannot match reserved names

R2020a: Improved performance when assigning elements by subscripting into table variables

R2019b: Variable names can contain leading and trailing whitespace characters

R2019b: Variable names and dimension names must be unique

R2019b: Improved performance when assigning elements by subscripting into large table variables

`var1,...,varN` — Input variables

`sz` — Size of preallocated table

`varTypes` — Data types of preallocated variables

`VariableNames` — Variable names

`RowNames` — Row names

`DimensionNames` — Dimension names

`DimensionNames` — Dimension names

`RowNames` — Row names

`Description` — Table description

`UserData` — Additional table information

`VariableNames` — Variable names

`VariableTypes` — Variable data types

`VariableDescriptions` — Variable descriptions

`VariableUnits` — Variable units

`VariableContinuity` — Status as continuous or discrete variables

`CustomProperties` — Customized metadata of table and its variables

R2024b: `VariableTypes` property of tables and timetables specifies the data types of their variables