MATLAB: How can i change x to (x+h)

replacing

This is my function, f(x)=x^2 – 4 and f(x+h)=(x+h)^2 – 4

f=@(x) x.^2- 4;

f=@(x+h) x.^2- 4 (this gives me error)

How can i write f(x+h) ?

I am not certain what problem you are having. You have to define all the values you pass to your function as arguments before calling your function.

Example —

f = @(x) x.^2- 4;
h = 1E-8;
dfdx = @(f,x,h) (f(x+h) - f(x))./h;
x = 4;
fval = f(x)
derv = dfdx(f,x,h)

Yusuke - if x is the input parameter to your function h, then you must pass this into f and g as well. So instead of

 h = @(x) (f+5*g)/(2*f*g);

you would write

 h = @(x) (f(x)+5*g(x))/(2*f(x)*g(x));

Try the above and see what happens!

You can use round()

x=4.21;
h=0.001;
f=@(x) x^3 + 8*x^2 + 23*x +3;
f2_prime = (round(f(x+h),4)-2*f(x)+round(f(x-h),4))/(h^2);