Diff does not work with symmatrix

Consider the following very simple example:

syms a x [1,1] matrix
diff(x .^ (symmatrix(eye(1)) - a), x)

ans = 

The output of the function shoud be simply:

(symmatrix(eye(1)) - a)*x.^-a

while instead is returned exactly the same command of the input.

Is it a bug? Do you know any turn around?

Thank you

[Torsten]

What is your real application ?

Answer 1

[Matt J]

Element-wise exponentiation is not a standard matrix algebra operation. I imagine it is for that reason that symmatrix.diff() doesn't support it. Workaround:

syms a x [3,3]
F_vec = reshape(x .^ (eye(3) - a), [], 1);
dF_vec = jacobian(F_vec, x(:));
dF = reshape(diag(dF_vec), 3, 3)

dF = 

[GIOSUÉ]

Thank you for your answer.