Register to reply

Derivative function in matlab

by Link-
Tags: derivative, function, matlab
Share this thread:
Link-
#1
May1-08, 11:26 PM
P: 98
I wrote a user-defined function in matlab that is supposed to take the derivative of a function f(x) in the point that correspond to (x,f(x)). Here's the code
function [fprime]=numderivative(f,x,h,tol)

hd=h*10^-1;
hh=h;
hhdd=hd;
itnum=numel(x);
error=tol+1;
for ii=1:itnum
    while error>tol
        fprime1=(f(x(ii)+h)-f(x(ii)))/h;
        fprime2=(f(x(ii)+hd)-f(x(ii)))/hd;
        error=abs(fprime1-fprime2);
        h=h*10^-1;
        hd=h*10^-1;
    end
    fprime(ii)=fprime1;
    h=hh;
    hd=hhdd;
    error=tol+1;
end
Obviously if you insert a real small tolerance (f(x(ii)+h)-f(x(ii))) would be zero even if the derivative is not zero. I'm trying to come up with something but I just don't know what to do.
Need help.

Thanks
link
Phys.Org News Partner Science news on Phys.org
Climate change increases risk of crop slowdown in next 20 years
Researcher part of team studying ways to better predict intensity of hurricanes
New molecule puts scientists a step closer to understanding hydrogen storage

Register to reply

Related Discussions
Matlab Derivative Approximation Math & Science Software 1
Matlab function Math & Science Software 2
Matlab mex-function Math & Science Software 0
Matlab function HW help please Math & Science Software 1
Matlab Second Derivative Ploting Problem Math & Science Software 3