importdata - Load data from file - MATLAB (original) (raw)

Syntax

Description

[A](#btk7vi1-1-A) = importdata([filename](#btk7vi1-1-filename)) loads data into array A.

[A](#btk7vi1-1-A) = importdata('-pastespecial') loads data from the system clipboard rather than from a file.

[A](#btk7vi1-1-A) = importdata(___,[delimiterIn](#btk7vi1-1-delimiterIn))interprets delimiterIn as the column separator in ASCII file, filename, or the clipboard data. You can use delimiterIn with any of the input arguments in the above syntaxes.

[A](#btk7vi1-1-A) = importdata(___,[delimiterIn](#btk7vi1-1-delimiterIn),[headerlinesIn](#btk7vi1-1-headerlinesIn)) loads data from ASCII file, filename, or the clipboard, reading numeric data starting from line headerlinesIn+1.

example

[[A](#btk7vi1-1-A),[delimiterOut](#btk7vi1-1-delimiterOut),[headerlinesOut](#btk7vi1-1-headerlinesOut)] = importdata(___) additionally returns the detected delimiter character for the input ASCII file in delimiterOut and the detected number of header lines in headerlinesOut, using any of the input arguments in the previous syntaxes.

example

Examples

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Import and display the sample image, ngc6543a.jpg.

A = importdata('ngc6543a.jpg'); image(A)

Figure contains an axes object. The axes object contains an object of type image.

The output, A, is class uint8 because the helper function, imread, returns empty results for colormap and alpha.

Using a text editor, create a space-delimited ASCII file with column headers called myfile01.txt.

Day1 Day2 Day3 Day4 Day5 Day6 Day7 95.01 76.21 61.54 40.57 5.79 20.28 1.53 23.11 45.65 79.19 93.55 35.29 19.87 74.68 60.68 1.85 92.18 91.69 81.32 60.38 44.51 48.60 82.14 73.82 41.03 0.99 27.22 93.18 89.13 44.47 17.63 89.36 13.89 19.88 46.60

Import the file, specifying the space delimiter and the single column header.

filename = 'myfile01.txt'; delimiterIn = ' '; headerlinesIn = 1; A = importdata(filename,delimiterIn,headerlinesIn);

View columns 3 and 5.

for k = [3, 5] disp(A.colheaders{1, k}) disp(A.data(:, k)) disp(' ') end

Day3 61.5400 79.1900 92.1800 73.8200 17.6300

Day5 5.7900 35.2900 81.3200 0.9900 13.8900

Using a text editor, create a comma-delimited ASCII file called myfile02.txt.

Import the file, and display the output data and detected delimiter character.

filename = 'myfile02.txt'; [A,delimiterOut]=importdata(filename)

A =

 1     2     3
 4     5     6
 7     8     9

delimiterOut =

Copy the following lines to the clipboard. Select the text, right-click, and then select .

Import the clipboard data into MATLAB® by typing the following.

A = importdata('-pastespecial')

Input Arguments

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Name and extension of the file to import, specified as a character vector or a string scalar. If importdata recognizes the file extension, it calls the MATLAB helper function designed to import the associated file format (such as load for MAT-files or xlsread for spreadsheets). Otherwise, importdata interprets the file as a delimited ASCII file.

For ASCII files and spreadsheets, importdata expects to find numeric data in a rectangular form (that is, like a matrix). Text headers can appear above or to the left of the numeric data, as follows:

Column headers or file description text at the top of the file, above the numeric data.
Row headers to the left of the numeric data.

Example: 'myFile.jpg'

Data Types: char | string

Column separator character, specified as a character vector or a string scalar. The default character is interpreted from the file. Use '\t' for tab.

Example: ','

Example: ' '

Data Types: char | string

Output Arguments

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Data from the file, returned as a matrix, multidimensional array, or scalar structure array, depending on the characteristics of the file. Based on the file format of the input file, importdata calls a helper function to read the data. When the helper function returns more than one nonempty output, importdata combines the outputs into a struct array.

This table lists the file formats associated with helper functions that can return more than one output, and the possible fields in the structure array, A.

File Format	Possible Fields	Class
MAT-files	One field for each variable	Associated with each variable.
ASCII files and Spreadsheets	data textdata colheaders rowheaders	For ASCII files, data contains a double array. Other fields contain cell arrays of character vectors. textdata includes row and column headers.For spreadsheets, each field contains a struct, with one field for each worksheet.
Images	cdata colormap alpha	See imread.
Audio files	data fs	See audioread.

The MATLAB helper functions for most other supported file formats return one output. For more information about the class of each output, see the functions listed in Supported File Formats for Import and Export.

If the ASCII file or spreadsheet contains either column or row headers, but not both, importdata returns a colheaders or rowheaders field in the output structure, where:

colheaders contains only the last line of column header text. importdata stores all text in the textdata field.
rowheaders is created only when the file or worksheet contains a single column of row headers.

Detected column separator in the input ASCII file, returned as a character vector.

Tips

To import ASCII files with nonnumeric characters outside of column or row headers, including columns of character data or formatted dates or times, usereadtable instead ofimportdata.

Version History

Introduced before R2006a