I'll give the same answer as on StackOverflow:
MATLAB Coder does not currently support sparse matrices.
Depending upon the size of the data, you may consider converting the inputs to full matrices before calling your MEX function.
If the purpose of generating a MEX function is to speed up parts of your code, you could consider generating MEX functions for the functions in your code which do not require sparse and call those from your other MATLAB code. This way, you could accelerate parts of the code and still use sparse where required.
