I am taking the derivative of a function with respect to another function, e.g.
D[g[f[x,y]],f[x,y]]
This outputs g'(f(x,y))
, as expected. How can I specify a rule for this derivative?
I've tried the following:
Derivative[g[f[x_,y_]][f[x_, k_]]] := f[y, k]
but apparently this isn't the output of D[]
.
Any ideas?
Derivative[g[f[x_, y_]][f[x_, k_]]] := g'[f[y, k]]
$\endgroup$