How to load and import a .mat file?

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Omar Mfarij
Omar Mfarij on 29 Nov 2021
Answered: Rik on 29 Nov 2021
Hi all,
I'm having a problem to load and read my ```mydata.mat``` in Matlab.
The structure is 1x1 with 2 fields data and hdr (header).
So I'm using the following syntax:
[data, hdr] = load("mydata.mat", "hdr9", "hdr10");
What I am doing that, I load the data and pick only the last 2 columns.
However, I am facing an error running the code:
>> [data, hdr] = load("mydata.mat", "hdr9", "hdr10");
Error using load
Too many output arguments.
And if I want to load without picking up the last 2 columns, it will give me the same error.
>> [data, hdr] = load("mydata.mat");
Error using load
Too many output arguments.
What is my mistake? And are there other ways to load and import the data?
Thank you!

Answers (1)

Rik
Rik on 29 Nov 2021
As the documentation explains, using load with output arguments will return a struct.
help load
LOAD Load data from MAT-file into workspace. S = LOAD(FILENAME) loads the variables from a MAT-file into a structure array, or data from an ASCII file into a double-precision array. Specify FILENAME as a character vector or a string scalar. For example, specify FILENAME as 'myFile.mat' or "myFile.mat". S = LOAD(FILENAME, VARIABLES) loads only the specified variables from a MAT-file. Specify FILENAME and VARIABLES as character vectors or string scalars. When specifying VARIABLES, use one of the following forms: VAR1, VAR2, ... Load the listed variables. Use the '*' wildcard to match patterns. For example, load('A*') loads all variables that start with A. '-regexp', EXPRESSIONS Load only the variables that match the specified regular expressions. For more information on regular expressions, type "doc regexp" at the command prompt. S = LOAD(FILENAME, '-mat', VARIABLES) forces LOAD to treat the file as a MAT-file, regardless of the extension. Specifying VARIABLES is optional. S = LOAD(FILENAME, '-ascii') forces LOAD to treat the file as an ASCII file, regardless of the extension. LOAD(...) loads without combining MAT-file variables into a structure array. LOAD ... is the command form of the syntax, for convenient loading from the command line. With command syntax, you do not need to enclose inputs in single or double quotation marks. Separate inputs with spaces instead of commas. Do not use command syntax if FILENAME is a variable. Notes: If you do not specify FILENAME, the LOAD function searches for a file named matlab.mat. ASCII files must contain a rectangular table of numbers, with an equal number of elements in each row. The file delimiter (character between each element in a row) can be a blank, comma, semicolon, or tab. The file can contain MATLAB comments. Examples: gongStruct = load('gong.mat') % All variables load('handel.mat', 'y') % Only variable y load('accidents.mat', 'hwy*') % Variables starting with "hwy" load('topo.mat', '-regexp', '\d') % Variables containing digits % Using command form load gong.mat load topo.mat -regexp \d load 'hypothetical file.mat' % Filename with spaces See also SAVE, MATFILE, WHOS, CLEAR, REGEXP, IMPORTDATA, UIIMPORT. Documentation for load doc load Other functions named load COM/load cstprefs.tbxprefs/load
So what you need to do is loading your mat file to a struct and then extract the variables:
S=load("mydata.mat");
[data,hdr]=deal(S.data,S.hdr);

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