Differential of a User-defined Function (Matlab)

Hi,

How might I make my script perform differentiation on a user-defined function? I also want the function and its derivative (in the form of a function) to be applied throughout the script, say in the forms of f and f' respectively, which I believe requires str2func.

Example: The user is prompted for an f(x). He enters x^3. Then both x^3 and 3*x^2 are applied in the place of f and f' throughout the script.

Thanks in advance!

Answer 1

[Walter Roberson]

It is tedious and error-prone to write your own differentiation operation. For example, what if the user entered Ei(GAMMA(hypergeom([1],[2,2],x))) -- how would you differentiate that?

If you have MuPad it is much easier to get MuPad to differentiate for you. You would not use str2func() for that. You might, though, use

fprime = matlabFunction(diff(sym('x^3')));

Note: it is not allowed to use f' as a variable name in MATLAB.