Invalid data for plotting(using a function)

Hello, I'm trying to plot a function on matlab, I looked up a few answers but none of them work for me.

function f=larange2(func,n)
funky=@(x) (1/(1+x^2));
xi=linspace(-1,1,n);
for i=1:n
    yi(i)=func(xi(i));
end
value=1;
zi=linspace(-1,1,100);
l=0;
ziy=[];
valuel=0;
for z=1:100
for i=1:n
    value=1;
    for c=1:n
        if c~=i
            value=value*((zi(z)-xi(c))/(xi(i)-xi(c)));
        end

              if c==n
                  ziy(z)=(value*yi(i));
              end

      end
  end
  end       
      for i=1:length(ziy)
      valuel=valuel+ziy(i);
  end
  plot(zi,ziy,xi,func);
  f=valuel;
  end

func is function passed in from another code which is

   func=@(x) 1/(1+x^2);
  values=larange2(func,3);

SO how do I do this valid, I tried defining the expression in the function itself but that still didn't work.

[Walter Roberson]

In your "for c" loop, what is to be done if c == i and c ~= n?