setdiff - Difference of two sets of data - MATLAB (original) (raw)

Difference of two sets of data

Syntax

Description

[C](#btcnv2b-1-C) = setdiff([A,B](#btcnv2b-1%5Fsep%5Fshared-AB)) returns the data in A that is not in B, with no repetitions.C is in sorted order.

If A and B are tables or timetables, thensetdiff returns the rows from A that are not inB. For timetables, setdiff takes row times into account to determine equality, and sorts the output timetable C by row times.

example

[C](#btcnv2b-1-C) = setdiff([A,B](#btcnv2b-1%5Fsep%5Fshared-AB),[setOrder](#btcnv2b-1-setOrder)) returns C in a specific order. setOrder can be'sorted' or 'stable'.

example

[C](#btcnv2b-1-C) = setdiff([A,B](#btcnv2b-1%5Fsep%5Fshared-AB),___,'rows') and`C` = setdiff(`A,B`,'rows',___) treat each row of A and each row of B as single entities and return the rows from A that are not in B, with no repetitions. You must specify A and B and optionally can specify setOrder.

The 'rows' option does not support cell arrays, unless one of the inputs is either a categorical array or a datetime array.

[[C](#btcnv2b-1-C),[ia](#btcnv2b-1-ia)] = setdiff(___) also returns the index vector ia using any of the previous syntaxes.

Generally, C = A(ia).
If the 'rows' option is specified, then C = A(ia,:).
If A and B are tables or timetables, thenC = A(ia,:).

example

[[C](#btcnv2b-1-C),[ia](#btcnv2b-1-ia)] = setdiff([A,B](#btcnv2b-1%5Fsep%5Fshared-AB),'legacy') and[`C`,`ia`] = setdiff(`A,B`,'rows','legacy') preserve the behavior of the setdiff function from R2012b and prior releases.

The 'legacy' option does not support categorical arrays, datetime arrays, duration arrays, tables, or timetables.

example

Examples

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Define two vectors with values in common.

A = [3 6 2 1 5 1 1]; B = [2 4 6];

Find the values in A that are not in B.

Define two tables with rows in common.

A = table([1:5]',['A';'B';'C';'D';'E'],logical([0;1;0;1;0]))

A=5×3 table Var1 Var2 Var3 ____ ____ _____

 1       A      false
 2       B      true 
 3       C      false
 4       D      true 
 5       E      false

B = table([1:2:10]',['A';'C';'E';'G';'I'],logical(zeros(5,1)))

B=5×3 table Var1 Var2 Var3 ____ ____ _____

 1       A      false
 3       C      false
 5       E      false
 7       G      false
 9       I      false

Find the rows in A that are not in B.

C=2×3 table Var1 Var2 Var3 ____ ____ _____

 2       B      true 
 4       D      true

Define two vectors with values in common.

A = [3 6 2 1 5 1 1]; B = [2 4 6];

Find the values in A that are not in B as well as the index vector ia, such that C = A(ia).

Define a table, A, of gender, age, and height for five people.

A = table(['M';'M';'F';'M';'F'],[27;52;31;46;35],[74;68;64;61;64],... 'VariableNames',{'Gender' 'Age' 'Height'},... 'RowNames',{'Ted' 'Fred' 'Betty' 'Bob' 'Judy'})

A=5×3 table Gender Age Height ______ ___ ______

Ted        M       27       74  
Fred       M       52       68  
Betty      F       31       64  
Bob        M       46       61  
Judy       F       35       64

Define a table, B, with the same variables as A.

B = table(['F';'M';'F';'F'],[64;68;62;58],[31;47;35;23],... 'VariableNames',{'Gender' 'Height' 'Age'},... 'RowNames',{'Meg' 'Joe' 'Beth' 'Amy'})

B=4×3 table Gender Height Age ______ ______ ___

Meg       F         64      31 
Joe       M         68      47 
Beth      F         62      35 
Amy       F         58      23

Find the rows in A that are not in B, as well as the index vector ia, such that C = A(ia,:).

C=4×3 table Gender Age Height ______ ___ ______

Judy      F       35       64  
Ted       M       27       74  
Bob       M       46       61  
Fred      M       52       68

The rows of C are in sorted order first by Gender and next by Age.

Define two matrices with rows in common.

A = [7 9 7; 0 0 0; 7 9 7; 5 5 5; 1 4 5]; B = [0 0 0; 5 5 5];

Find the rows from A that are not in B as well as the index vector ia, such that C = A(ia,:).

[C,ia] = setdiff(A,B,'rows')

Use the setOrder argument to specify the ordering of the values in C.

Specify 'stable' or 'sorted' when the order of the values in C are important.

A = [3 6 2 1 5 1 1]; B = [2 4 6]; [C,ia] = setdiff(A,B,'stable')

Alternatively, you can specify 'sorted' order.

[C,ia] = setdiff(A,B,'sorted')

Define two vectors containing NaN.

A = [5 NaN NaN]; B = [5 NaN];

Find the set difference of A and B.

setdiff treats NaN values as distinct.

Create a cell array of character vectors, A.

A = {'dog','cat','fish','horse'};

Create a cell array of character vectors, B, where some of the vectors have trailing white space.

B = {'dog ','cat','fish ','horse'};

Find the character vectors in A that are not in B.

C = 1×2 cell {'dog'} {'fish'}

setdiff treats trailing white space in cell arrays of character vectors as distinct characters.

Create a character vector, A.

A = ['cat';'dog';'fox';'pig']; class(A)

Create a cell array of character vectors, B.

B={'dog','cat','fish','horse'}; class(B)

Find the character vectors in A that are not in B.

C = 2×1 cell {'fox'} {'pig'}

The result, C, is a cell array of character vectors.

Use the 'legacy' flag to preserve the behavior of setdiff from R2012b and prior releases in your code.

Find the difference of A and B with the current behavior.

A = [3 6 2 1 5 1 1]; B = [2 4 6]; [C1,ia1] = setdiff(A,B)

Find the difference of A and B, and preserve the legacy behavior.

[C2,ia2] = setdiff(A,B,'legacy')

Input Arguments

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Order flag, specified as 'sorted' or 'stable', indicates the order of the values (or rows) in C.

Flag	Description
'sorted'	The values (or rows) in C return in sorted order as returned by sort.ExampleC = setdiff([4 1 3 2 5],[2 1],'sorted')C = 3 4 5
'stable'	The values (or rows) in C return in the same order as inA.ExampleC = setdiff([4 1 3 2 5],[2 1],'stable')C = 4 3 5

Data Types: char | string

Output Arguments

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Difference of A and B, returned as a vector, matrix, table, or timetable. If the inputs A and B are tables or timetables, then the order of the variables in C is the same as the order of the variables in A.

The following describes the shape of C when the inputs are vectors or matrices and when the 'legacy' flag is not specified:

If the 'rows' flag is not specified and A is a row vector, then C is a row vector.
If the 'rows' flag is not specified and A is not a row vector, then C is a column vector.
If the'rows' flag is specified, then C is a matrix containing the rows of A that are not inB.
If all the values (or rows) of A are also in B, then C is an empty matrix.

The class of C is the same as the class of A, unless:

A is a character array and B is a cell array of character vectors, in which case C is a cell array of character vectors.
A is a character vector, cell array of character vectors, or string, and B is a categorical array, in which case C is a categorical array.
A is a cell array of character vectors or single character vector and B is a datetime array, in which case C is a datetime array.
A is a character vector or cell array of character vectors andB is a string array, in which case C is a string array.

Index to A, returned as a column vector when the'legacy' flag is not specified. ia identifies the values (or rows) in A that are not in B. If there is a repeated value (or row) appearing exclusively in A, thenia contains the index to the first occurrence of the value (or row).

Tips

To find the set difference with respect to a subset of variables from a table or timetable, you can use column subscripting. For example, you can usesetdiff(A(:,_`vars`_),B(:,_`vars`_)), where vars is a positive integer, a vector of positive integers, a variable name, a cell array of variable names, or a logical vector. Alternatively, you can usevartype to create a subscript that selects variables of a specified type.

Extended Capabilities

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

The 'stable' and 'legacy' options are not supported.
Inputs of type 'char' are not supported.
Ordinal categorical arrays are not supported.

For more information, see Tall Arrays.

Usage notes and limitations:

Code generation does not support cell arrays for the first or second arguments.
When you do not specify the 'rows' option:
- Inputs A and B must be vectors. If you specify the 'legacy' option, then inputs A andB must be row vectors.
- The first dimension of a variable-size row vector must have fixed length 1. The second dimension of a variable-size column vector must have fixed length 1.
- Do not use [] to represent the empty set. Use a 1-by-0 or 0-by-1 input, for example, zeros(1,0), to represent the empty set.
- If you specify the 'legacy' option, then empty outputs are row vectors, 1-by-0. They are never 0-by-0.
When you specify both the 'legacy' and 'rows' options, the output ia is a column vector. If ia is empty, then it is 0-by-1. It is never 0-by-0, even if the output C is 0-by-0.
When the setOrder is not 'stable' or when you specify the 'legacy' option, the inputs must already be sorted in ascending order. The first output, C, is sorted in ascending order.
Complex inputs must be single or double.
When one input is complex and the other input is real, do one of the following:
- Set setOrder to 'stable'.
- Sort the real input in complex ascending order (by absolute value). Suppose the real input is x. Use sort(complex(x))orsortrows(complex(x)).
See Code Generation for Complex Data with Zero-Valued Imaginary Parts (MATLAB Coder).

The setdiff function supports GPU array input with these usage notes and limitations:

The 'legacy' flag is not supported.
64-bit integers are not supported.

For more information, see Run MATLAB Functions on a GPU (Parallel Computing Toolbox).

Usage notes and limitations:

The 'legacy' flag is not supported.
Table, timetable, categorical, datetime and duration inputs are not supported.
Inputs of type char and string are not supported when A or B is a cell array of character vectors. Convert cell arrays of character vectors input arguments to string arrays instead.

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

Version History

Introduced before R2006a