Subscripting into an mxArray is not supported for code generation - I think it's the colon that's the issue

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Mads 2016-12-14

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评论： Mads 2016-12-15

This part of my code

    V = zeros(n,m+1);
    V(:,1) = (1/beta)*w;

is giving me an error "Subscripting into an mxArray is not supported for code generation", when I use MATLAB Coder to create a Mex file. But if I can't fill V that way and so forth what is the correct way to do it? Other places I get "Unexpected MATLAB operator" and the MATLAB Coder points me to the ":"

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Answer 1

James Tursa 2016-12-14

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https://ww2.mathworks.cn/matlabcentral/answers/316850-subscripting-into-an-mxarray-is-not-supported-for-code-generation-i-think-it-s-the-colon-that-s-th#answer_247204

在 MATLAB Online 中打开

What happens if you use explicit indexes?

V(1:n,1) = (1/beta)*w;

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Mads 2016-12-15

在 MATLAB Online 中打开

Apparently, it is not the issue after all. I did a test earlier in the code:

test= rand(5,1);
test2 = zeros(5,2);
test2(:,1) = test;
test2(1:5,2) = 2*test;

and it passes, so basically, the original error is misleading. So there is a main function and a subfunction. And things start to go wrong from the point where I call the subfunction in which the original error was, although, I conduct the same test in the subfunction and it passes. So I'm left without a clue. I worry there is one error leading to other errors...

Mads 2016-12-15

I finally managed to locate the seeding error of all other errors. I'm disappointed by the fact that I was not allowed to use spdiags() even though I made it extrinsic ("coder.extrinsic('spdiags')"). This has resulted in a workaround that finally has made the MEX slower than the native matlab script because I at some point am forced to use non-sparse matrices...

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