how can i change x to (x+h)?

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) ?

Answer 1

[Star Strider]

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)

Answer 2

[Adam]

It's the same function definition, you just pass in

x + h

instead of

x

assuming you have x and h defined at the point you call the function.

Or you could define

f = @(x,h) ( x + h )^2 - 4

if you prefer.

[Steven Lord]

Or you could reuse f in defining the next function.

f = @(x) x.^2- 4;
g = @(x, h) f(x+h);

Check that they give the same result on some sample data.

x = 1:10;
h = 1;
y1 = f(x+h)
y2 = g(x, h)