How to load and import a .mat file?

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!

Answer 1

[Rik]

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);