Need Help implementing an equation

HI, I intend to implement this equation .....

f(x)=[(1/N)*rect(x/a)]*{summation n=1->N [sin(k(n).*x)]}

where, N = 22; x = x1i1+x2i2 (1i,i2 are unit vectors in x and y direction and x1,x2 are x,y coordinates)

Now, I have implemented the equation 70 %, can some one validate if I have been doing right, plus suggest how should I go ahead.

 clear all; close all;
 x1 = [-50:50]
 x2 = [-50:50]

 k1 = [550:22:1012]
 k2 = [550:22:1012]

 b = zeros(2, 101);

 for m = 1:101,
    p=0

    for n = 1:22
        k = [k1(n),k2(n)]
        x = [x1(m),x2(m)]
        p = p+sin(k.*x) 
        mx=hypot(x1,x2)

    end

    b(:,m) = p

    rect=@(mx,a) ones(1,numel(x)).*(abs(x)<a/2)            % Rect Function
    q=rect(mx,50)

 end