You need to define x as an array, when you sustitue x in the function f, you will get output array y which is of same dimension like x. And after you can index.
EXamples:
f = @(x) sin(x) ;
x = linspace(0,2*pi) ;
y = f(x) ;
plot(x,y)
for i = 1:10
[x(i) y(i)]
end
If you are planning to use a loop (to learn).
f = @(x) sin(x) ;
x = linspace(0,2*pi) ;
y = f(x) ;
n = length(x) ;
y = zeros(1,n) ;
for i = 1:n
y(i)= f(x(i)) ;
end
plot(x,y)
