Having trouble creating a conditional function

Hi it's my first time posting here

I am trying to create a conditional function

x = -1:0.1:1;

f = x.^2.*sin(pi.*x);

So the conditions are

if f>=0

g = f

elseif f<0

g = 0

I have tried to create separate vectors containing the index that give positive respespective negative values of f and then create an if statement that looked something like this

if f == f(a)
g = f(a)
%where a is the index that give positive values
elseif f == f(b)
g = 0
end 
but it doesn't seem to work at all
what am I doing wrong?

Answer 1

[KL]

Just use

 x = -1:0.1:1;
 f = x.^2.*sin(pi.*x);

and then to create g based on f

 g = f;
 g(g<0)=0;

[Michael Bettar]

wow I really have overcomplicated the answer

thanks for help!

[Walter Roberson]

g = max(0, f);