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Ved
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MATLAB Coder - How to use "save" command

Asked by Ved
on 18 Mar 2015
Latest activity Commented on by Mike Hosea
on 20 Mar 2015
I am using MATLAB (R2013a) Coder to generate the appropriate C++ files. I am unable to use the 'save' command when I am trying to save my processed matrices. Cutting the chase, if I have a simple function like the following (that just saves the variable as .mat file, and also returns the same),
function a = savefun( a )
%#codegen
save('a','a');
end
then I am having trouble generating the appropriate .cpp/.h files using Codegen. Here's a screens shot
.
Any help will be appreciated.

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1 Answer

Answer by Mike Hosea
on 19 Mar 2015

Unfortunately, the SAVE command is not supported for code generation, and it doesn't make sense to call it as an extrinsic function. Since you are running R2013a, you should be able to use FOPEN, FCLOSE, and FPRINTF to write a text file with your data in it. Note that FPRINTF for code generation will require you to write your array elements with a loop (or loops), since it doesn't support the automatic looping that MATLAB's FPRINTF does. It will be more cumbersome to use the text files back in the MATLAB environment, but it should work.
The only alternative I might suggest, if your need is limited to returning intermediate stages for, say, debugging purposes, is to use ASSIGNIN as an extrinsic function.
function a = dosomething( a )
%#codegen
coder.extrinsic('assignin');
% Input changes, and we want to remember this step.
a = a/2;
assignin('base','a1',a);
% Array changes again. Remember this value.
a = a + 1;
assignin('base','a2',a);
% Array changes again, but this is the return value.
a = cos(a);
Then your calling program can use the SAVE command to write mat files if you need them.

  1 Comment

Ah, I just realized how to do it in MATLAB (not for standalone code generation). You need a function
function mysave(varname,value)
assignin('base',varname,value)
save(varname,varname);
This is a .m file that you will need on the MATLAB path. You won't generate code for it. Then you call this function extrinsically in your own code. You can use coder.extrinsic for it, as above, or just
feval('mysave','a',a);
when you would have written
save('a','a');

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