MATLAB: What functionalDerivative returns is a 1*1 symfun, not a vector

Question

Hi guys,

I am trying the codes

syms u(x) v(x)

H = u^2*diff(v,x)+v*diff(u,x,x);

D = functionalDerivative(H,[u v])

at https://au.mathworks.com/help/symbolic/functionalderivative.html

Actually, the D returned by functionalDerivative is a 1*1 symfun, but a 1 * 2 vector of symbolic functions.

So how to return a 1*2 vector?

Many thanks.

Answer 1

syms u(x) v(x)
H = u^2*diff(v,x)+v*diff(u,x,x);
D(1) = functionalDerivative(H,u)
D(2) = functionalDerivative(H,v)