reshape() error in the function created by matlabFunction()

matlabFunction() has generated for me AmplAndDers() to be used in fminunc(). The very first objective function evaluation fails:

Error using reshape

Number of elements must not change. Use [] as one of the size inputs to automatically calculate the appropriate size for that dimension.

Error in AmplAndDers (line 93)

Hess = reshape([-t2.*t3.*t4. ... .*(3.0./4.0)],[4,4]);

The signature of the function is:

function [Ampl,GradA,Hess] = AmplAndDers(C1_0,C2_0,R1_0,R2_0,w,x1,x2,x3,x4)

I call it with a w being an array. Two other outputs are returned correctly. I do not understand what does the above suggestion mean:

Use [] as one of the size inputs to automatically calculate the appropriate size for that dimension.

If I manually change the above reshape() call to end with:

...*(3.0./4.0)],[4,4,length(w)]);

the program runs OK.

How can avoid the manual intervention?

[Valeri Aronov]

Having no luck with the suggestions I dare to submit it is a bug hoping to get a response from Staff. Afterall the produced message is unclear: what does it mean to 'Use []' in the code that MATLAB generates.?

[Stephen23]

"The very first objective function evaluation fails:"

Can you please show the exact code you use when supplying that function to FMINUNC.

[Valeri Aronov]

This is the script that creates the function in question:

syms s

syms C1 C2 R1 R2 w real

syms C1_0 C2_0 R1_0 R2_0 real

syms T(s, C1, C2, R1, R2)

T(s, C1, C2, R1, R2) = 1/(C1*C2*R1*R2*s^2 + (C2*R1 + C2*R2)*s + 1);

A = abs(T(1j*w, C1, C2, R1, R2));

A = rewrite(A, 'sqrt')

syms x1 x2 x3 x4 real

x=[x1,x2,x3,x4];

A = subs(A, [C1, C2, R1, R2], [C1_0, C2_0, R1_0, R2_0] .*x);

Ampl = A;

GradA = gradient(A, x);

Hess = hessian(A, x);

x0 = [0.1e-6, 1.5e-9, 16000, 11000];

f = logspace(1,5,101);

A_Init = double(abs(T(1j*f, x0(1), x0(2), x0(3), x0(4))));

% Covert symbolic functions to the function

matlabFunction(Ampl, GradA, Hess, 'File', 'AmplAndDers');

This how I tried to follow MATLAB hint and failed:

% matlabFunction(Ampl, GradA, Hess, 'File', 'AmplAndDers', 'Vars', {C1_0,C2_0,R1_0,R2_0,w[],x1,x2,x3,x4});

Thanks

[Valeri Aronov]

Oops. The call is here:

function [x, fval] = OptimizeFilter(A0, f, x0)

options = optimoptions('fminunc','Algorithm','trust-region','SpecifyObjectiveGradient',true, HessianFcn','objective');

[x,fval,exitflag,output] = fminunc(@Target, [1,1,1,1], options)

function y = Target(x)

[aCurrent, GradW, HessW] = AmplAndDers(x0(1), x0(2), x0(3), x0(4), f, x(1), x(2), x(3), x(4));

...

end

end

Answer 1

[Valeri Aronov]

The error is known to MATLAB and will be fixed in the future

Answer 2

[KSSV]

Read the documentation of reshape and understand it. The error is clear, you are trying to create extra elements than present in the array while reshaping.

Example:

A = rand(1,25) ;
B = reshae(A,5,5) ; % 5*5 = 25, no error as same elements present 
C = reshape(A,6,5) ; % 6*5 = 30, error as A as 30 elements only. 

[Valeri Aronov]

The body of AmplAndDers() function and the reshape() call code in it is generated by matlabFunction(). I can't see how reading the documentation of reshape() can possibly help me. And, yes, the error is clear indeed.