B-Spline Basic function Matlab recursive - matlab

Question

I'm trying to make a B-Spline Function
first i set the variables and made the Knot vector
# cmpp.m
% Set variables
k = 3; % (8 mod 2 + 2 + 1)
p = k - 1; % Order = 2
n = 2*k - 1; % Control points = 5
l = n + p + 1; % Vector size n + p + 1 = 8
% Create the Knot vector
% Kv = [0 0 0 1 2 3 3 3] size = 8
knoten = 0; % set all knots to 0
Kv = [];
for j=1:1:l
Kv = [ Kv 0 ];
end
for i=1:1:l
if (i > n)
if (i <= n)
Kv(i) = knoten + 1;
knoten = knoten + 1;
else
Kv(i) = knoten;
end
else
Kv(i) = knoten;
end
end
then i worte a function to create the basic function
# f.m
function N = f(N,t,i,k,u,x,s)
if (u < x)
N(i,k) = ((((u-t(i)).*f(t,i,k-1,u+s,x,s)) / (t(i+k-1) - t(i))) + (((t(i+k)-u).*f(t,i+1,k-1,u+s,x,s)) / (t(i+k) - t(i+1))));
if ((u >= t(i)) && (u < t(i+1)))
N(i,1) = 1;
else
N(i,1) = 0;
end
end
end
and called it in cmpp.m
# cmpp.m
...
...
...
N = zeros(l,k);
x = (n+1) - (k-1);
s = 1;
N = [N f(N,Kv,1,k,0,x,s)];
but i get always this error in Matlab
>> cmpp
Subscripted assignment dimension mismatch.
Error in f (line 3)
N(i,k) = ((((u-t(i)).*f(t,i,k-1,u+s,x,s)) / (t(i+k-1) - t(i))) +
(((t(i+k)-u).*f(t,i+1,k-1,u+s,x,s)) / (t(i+k) - t(i+1))));
Error in cmpp (line 32)
N = [N f(N,Kv,1,k,0,x,s)]