codegen error: Conversion to struct from double is not possible

I am trying to convert Matlab legacy code into a C program. I went though the usual flows, but am having a build error that I do not understand:

Nfft = 8;
[~,coh] = size(h); // h = array of 168 elements;
display(coh); // displays 168
if mod(coh,Nfft)~=0,  
    h1 = [h zeros(1,Nfft-mod(coh,Nfft))];
else 
    h1 = h;
end

This works as expected in Matlab. But when I run it through codegen (after removing the display), I get an error at the line h1 = [h zeros(1,Nfft-mod(coh,Nfft))]; with the error message:

Conversion to struct from double is not possible.

I realize that in the matlab code, it doesn't go through this part of the code. (since 168%8 == 0).

Any ideas how to fix this?

EDIT: After some investigating, I realize that I am reading in h from a .mat file and this may be the reason. Is data read in from a .mat file considered to be a structure? If this is the case, then maybe I need to convert each element to a double first? Seems kind of hacky..

Answer 1

[Walter Roberson]

"Is data read in from a .mat file considered to be a structure?"

If you used

h = load('YourFile.mat')

then h would be a structure, containing one field for each variable that you loaded from the .mat file. If the only thing in that .mat file was a variable named 'h' then you would then address it as h.h

The general method to use is something like

filestruct = load('YourFile.mat');     %load into a structure
h = filestruct.h;                      %pull out a specific part of the structure.

[ChipMonk]

Yes this works! I was using:

h = coder.load('my_file.mat', 'my_file_var1');

Changed it to:

tmp = coder.load('my_file.mat');
h = tmp.my_file_var1;

Thank you@!