Chebyshev polynomials of the first kind

Hello everyone. I've been writing Chebyshev code but I have problem.

function pol=cheby(n,x)
toplam=0;
if(n==0)
    pol=1;
elseif(n==1)
    pol=x;
else
    for n=0:6
    pol=toplam + 2.*(x).*cheby(n-1,x)-cheby(n-2,x);
end
end

It goes to infinite recursion. When I do it one by one with elseif it works. How can I work it ? (I want to work it for n=0,1,2,3,4,5,6)

Answer 1

[David Goodmanson]

Hi Asli

If you get the do loop out of the code so that the three lines

 for n=0:6
 pol=toplam + 2.*(x).*cheby(n-1,x)-cheby(n-2,x);
 end

are just

pol=toplam + 2.*(x).*cheby(n-1,x)-cheby(n-2,x);

then cheby(n,x) it works correctly. Then you can call it in a for loop for different values of n.

And if you replace

pol = 1     with   pol=ones(size(x));

then the function will work with a vector of x values.