MATLAB: Can I control the column order of workspace variables saved to .mat format

columnsexportimportmatorderoriginoriginlabssave

I would like to save workspace variables to a .mat file and then open them up in Origin. Is there a way to control the order in which the variables appear in Origin's columns? Alternatively, how does MATLAB choose the column order when saving workspace variables? The variables (all vectors) I'm using have a variety of naming patterns and sizes (1 to 10,000 rows). I haven't found a reliable scheme as to how MATLAB orders these variables.

An example of the code I'm using is listed below:

SampleData_1 = (1:200)';
SampleData_2 = (1:2:200)';
SampleData_3 = (1:10:5000)';
save 'ExportTest.mat' SampleData_1 SampleData_2 SampleData_3;

After importing ExportTest.mat into Origin, the following variables appear from left to right: SampleData_1, SampleData_2 and SampleData_3. Can I force it to appear from left to right: SampleData_3, SampleData_1 and SampleData_2?

Best Answer

Undocumented behavior. Can't rely on anything about the internal order; all SAVE says is that can LOAD the file back and have what was stored returned. A test here of some local variables of

save file1.mat a b
save file2.mat b a
!fc /b file1.mat file2.mat

showed the only difference internally was the three positions in the internal header that record the timestamp--iow, internally Matlab wrote the two variables in the same order regardless of the order they were on the command line.

OTOH,

save file1.mat a
save file1.mat b -append
save file2.mat b
save file2.mat a -append

shows that the two files are different. This version probably works albeit even it would be relying on undocumented behavior.

Why don't you just write stream files with fprintf where you know you can control the content and order?

ERRATUM:

"...write stream files with fprintf ..."

That is/was intended to be fwrite of course... :(

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MATLAB: Saving everything in the workspace

You can use the command or the function syntax. If the variable names are the values of string variables then command syntax cannot be used.

Try

    >> save_test

it prints to the command window

      Name      Size            Bytes  Class     Attributes
      a         1x1                 8  double

where

    function save_test
        a = 1;
        b = 2;
        Save_Xallback
        whos -file save_test.mat
    end
    function Save_Xallback
        evalin( 'caller', 'save save_test.mat a' );
    end

Answer to the first comment:

The above is a hint rather than a complete answer. I don't exactly understand what you want to achieve. Variables of which workspace do you want to save? Outline a simple example in code. Some basics:

Workspaces

there is the base workspace and
each function has it own workspace

Callbacks

callbacks are "called" from the base workspace; the caller is the base. Thus, evalin( 'caller', ... ) and evalin( 'base', ... ) are equivalent in a callback function.

Command and Function syntax

save myfile.mat a
save( 'myfile.mat', 'a' )

"I'm thinking ... : evalin('caller','save save_test.mat variables')"

The variables of which workspace do you want to save?
Why did you introduce the function, Save_Callback?

"... save the workspace while in any function?"

there is no "the workspace". There are many.

I believe it is difficult to save the complete "state" of a running Matlab program. Special cases maybe.

MATLAB: Can I Load/Combine Vectors Data

number_of_mat_files = 2;
for iLoop=1:number_of_mat_files
    sMatFileName = ['file', num2str(iLoop), '.mat'];%construct mat file name using the file number
    Arr = load(sMatFileName);
    if iLoop==1
        FinalArr = Arr.a;%a is the name of the variable in the mat file
    else
        MaxTime = FinalArr(end,1);
        Arr = load(sMatFileName);
        Arr.a(:,1) = Arr.a(:,1)+MaxTime;
        FinalArr  = [FinalArr ;Arr.a];
    end
end

Best Answer

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MATLAB: Can I Load/Combine Vectors Data

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