How to link previous & next values to current values?

I've calculated values as follows for n=3 & k=3

%  Degree
    n = input('Degree of curve = ');
%  Order
    k = input('Order of curve = ');
%  No. of control points 
    No_of_Control_point = n+1
%   No_of_Knots
    m = n+k+1
%  Values_of knots as u_0, u_1, ...
    for i = 0:(m - 1);
        if i < k
            u = 0
        elseif (k <= i) && (i <= n)
            u = i-k+1
        else
            u = n-k+2
        end
    end
%  Finding N_i,k (u)...

Above coding gives 7 values of u as u=0,u=0,u=0,u=1,u=2,u=2 & u=2...& now I've to calculate a function [N_i,k(u)] for defined values for i = 0:5; (k = 3; it is constant) where if u_i<=u<=u_(i+1); N_i,k(u) = 1; else N_i,k(u) = 0 and so on... But I'm unable to understand that now to call u_i & u_(i+1) for calculating N_i,k(u). For good view see below...

% Finding N_i,k (u)...  
% Here k = 1 ...
   for i = 0:5;
     if (u_i<=u) && (u<=u_(i+1)
        N_i (u) = 1
     else
        N_i,k (u) = 0
     end
   end
% I'm unable to call u_i & u_(i+1)??

Can you help me please?