function N = blends(knots,u)

p = length(u);
n = length(knots) - 5;

N = zeros(n+4,4,p);

for j = 1:p
    for i = 1:n+4
        if (u(j) >= knots(i)) && (u(j) < knots(i+1))
            N(i,1,j) = 1.0;
        else
            N(i,1,j) = 0.0;
        end
    end
    
    for k = 2:4
        for i = 1:n+5-k
            N(i,k,j) = (u(j) - knots(i))*(N(i,k-1,j)/(knots(i+k-1) - knots(i))) + (knots(i+k) - u(j))*(N(i+1,k-1,j)/(knots(i+k) - knots(i+1)));
        end
    end
end