MATLAB: How to get the only variable in file .mat autoumaticly

automatic;loadvector

hello,

i am developping a function where i need a vector this one is going to be in a file .mat ,and in my function i can only call the file .mat.

Function FAngle(vectorfile)

load(vectorfile);

FAmax=max(vectorfile)

end

wha i want is getting the max value of my vector wich is in the file , so when i do like this i got a false value.i thinnk it is a value of the file structure and not the value of the vector in this file .mat

thank you for your help

Best Answer

Your function signature is incomplete. Hopefully, you do know how to write a function properly.

function FAmax = somename(vectorfile)
    %function documentation goes here
    %vectorfile: full path of mat file to load. The mat file must contain one variable only, and this variable must be a vector
    %FAmax: maximum value of the vector stored in the mat file.
    matcontent = load(vectorfile);  %load mat file into a structure. Each field of the structure is a variable of the mat file. See load documentation
    varnames = fieldnames(matcontent);  %get names of variables
    assert(numel(varnames) == 1, 'MAT file contains more than one variable');
    FA = matcontent.(varnames{1});
    assert(isvector(FA), 'The variable in the mat file is not a vector');
    FAmax = max(FA);
end

Related Solutions

MATLAB: How to save the contents of a struct to a .mat file

Solution

This is exactly what load does when it has an output variable: it loads into one structure, where each field is one of the variables that were saved in the .mat file. So when you save only one variable dataout, the output of load is a structure with one field: dataout (your structure, but it could be anything). You can access your structure in the usual way:

 S = load('file.mat');
 b = S.dataout;

Here is a complete working example of this:

>> old.a = 12.7;
>> old.b = NaN;
>> old.c = 999;
>> save('test.mat','old')
>> S = load('test.mat');
>> new = S.old; % <- yes, you need this line!
>> new.a
ans =  12.700

Alternative

As an alternative you can actually change the save call to get exactly the effect that you desire, by using the '-struct' option:

>> save('test.mat','-struct','old') % <- note -struct option
>> new = load('test.mat');
>> new.c
ans =  999

This simply places all of the fields of the input scalar structure as separate variables in the mat file. Read the help to know more.

MATLAB: Load structure array with a function and extract the variables

I did not understand exactly what you're trying to do. It sounds like you are trying to name your variables depending on the file that you load, which is never a good idea.

However, I can certainly explain the error message. The mat file that you are trying to load a file that contains a variable of type dataset. The version of matlab that you are using does not know what a dataset is. It's because either you're missing the required toolbox (e.g. there's a dataset type in the statistics and machine learning toolbox) or because it's a custom type for which you're missing the m file (in which case you need to ask whoever saved that mat file for the required m files).

In any case, without the required toolbox or necessary m file, you will not be able to load that mat file properly. You may be able to load part of the file using matfile but you'll always be missing the dataset.

Best Answer

Related Solutions

MATLAB: How to save the contents of a struct to a .mat file

MATLAB: Load structure array with a function and extract the variables

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