Why is there an error?

function chebyshev (a, b, numpolys)
t=a:0.1:b;
allp=zeros(numpolys, length(t));
for n=1:numploys
    x=(a+b)/2+(b-a)/2*cos((2*(1:n)-1)*pi/(2*n));
    y=(1)./(x.^2+1);
    allp(n,:)=newton(x, y, t);
end
plot (t, allp)
end
function p=newton(x,y,t)
    n=length(x);
    x=30;
    y=1.0803306e-44;
    t=[a,b];
    c=y;
    for k=2:n
   c(k:n)=(c(k:n)-c(k-1))./(x(k:n)-x(k-1));
    end
    p=c(n)*ones(size(t));
    for k=n-1:-1:1
        p=p.*(t-x(k))+c(k);
    end
end

Answer 1

[Wayne King]

The simple answer is your input argument is spelled numpolys in the function declaration, but you spell it numploys in the for loop.

But you have other problems, for example you have a,b internal to the subfunction newton(), but you don't pass those.