MatlabFunction error: Argument 'vars' failed validation isVars.

here In my program, I calculate the symbolic gradient and evaluate them with given values.However，when I enconter a error when using the MatlabFunction. The error says

Error using sym/matlabFunction>getOptions (line 500)
Argument 'vars' failed validation isVars.

Error in sym/matlabFunction (line 100)
opts = getOptions(args);

Error in mini_dist (line 54)
matlabFunction(dfb,'file',filename,'vars',b);

The related part of my program is

[b,fun,flag]    = fminunc(@cov,b0);
%dfb             = gradient(fcn,b);
nT = T_z + T_e;
B = sym('B', [nT, 1]);
temp = fcn(B);   %zt and et are not defined until fcn is run
v = [zt;et];
dfb             = jacobian(temp,v);
currdir = [pwd filesep]; % You may need to use currdir = pwd 
filename = [currdir,'gradient.m'];
matlabFunction(dfb,'file',filename,'vars',b);  % Line-54 %

And the full code and data see attachment

Also, a former related question is here

Thank you for your advice

Answer 1

[Walter Roberson]

You have

[b,fun,flag]    = fminunc(@cov,b0);

so your b is numeric.

You have

matlabFunction(dfb,'file',filename,'vars',b);  % Line-54 %

but your b is numeric.

You should possibly be passing in B or v rather than b.

When I tested your code before, the returned jacobian had only numeric entries and no variables; I did not test your current code. You need to think more about how your jacobian is to be used.