Recursive symbolic differentiation with anonymous functions

Question

0 个投票

This is closely related to an earlier post of mine, but i thought I should make it a separate thread, since it's not really the same topic

I'd like the commands

syms x lambda 
f = @(x)B(x);
g = @(x)lambda*C(x); 
h = @(x)f(x) - g(x);
diff(h,x)

to "go inside of h(x)" and differentiate both f and g, to return

diff(B(x), x) - lambda*diff(C(x), x)

Instead it returns

diff(f(x), x) - diff(g(x), x)

I get the answer I want if I use

syms x 
f = sym('B(x)')
g = sym('lambda*C(x)')
h = f - g; diff(h,x)

but this coding is less flexible than the former, since the argument 'x' is "hard-coded" into my functions, so I would have to use subs everytime I want to give my functions different arguments.

So in short, what I'm hoping for is the best of both worlds, the flexibility provided by anonymous functions plus the recursive (and other) properties provided when I use "sym"