How to solve this error "Attempt to extract field 'NormalizePathGains from 'mxArray'?

How to solve this error "Attempt to extract field 'NormalizePathGains' from 'mxArray'? Here is the code

ChanRD = zeros(K,block_size*Q);
coder.extrinsic('rayleighchan');
for j = 1:K

   CHANN = rayleighchan(T_s,F_D);
   CHANN.NormalizePathGains = 1;
   CHANN.ResetBeforeFiltering = 1;
   x = ones(1,Mc_Ber*Q*block_size);% known transmitted signal
   ChanRD(j,:) = filter(CHANN,x);

Answer 1

[Walter Roberson]

Before the loop, assign to CHANN a structure array with the proper fields and the maximum size that rayleighchan will allocate. Then the CHANN = rayleighchan(T_s,F_D) assignment will result in the data being pulled out of the mxArray into memory accessible to the function.

[Hs5555]

hi walter, I've encountered the same problem in the following code:

fitresult = fit(x,y, fit_1); % fit is a function of curve fitting toolbox
slope = fitresult.a;

how do I assign the variable 'fitresult' a structure with the proper fields and the maximum size and how can i find out how much memory to allocate?