How to form an aggregate from a random walk?

I am making a random walk function that starts at a given boundary point and runs the a walk until the 'particle' attaches to a seed particle at (0,0,0). The process is repeated for N number of particles and an aggregate or cluster forms. The method is fairly obvious and the variable that stores the coordinates of the aggregate is agg. I want to be able to see this plotted in 3D but my method isn't working. Thanks for any help.

function [x,y,z,agg] = DLARandWalk(n,dt,b)
% Random Walk Function

s = round(randn(3,n-1));
%  Direction is random.
dx = s(1,1:n-1);
dy = s(2,1:n-1);
dz = s(3,1:n-1);

x = zeros(1,n);
y = zeros(1,n);
z = zeros(1,n);

% Set intial position to Boundary
x(1) = -1*b;
y(1) = -1*b;
z(1) = -1*b;

%%Map Creation

%agg = zeros(b,b,b);
agg = zeros(3,n);

stuck = 0;

while stuck == 0

    for a = 2:n-1
        if abs(x(a-1)) <= b
            x(a) = x(a-1) + dx(a);
        else
            x(a) = sign(x(a-1))*b;
        end
        if abs(y(a-1)) <= b
            y(a) = y(a-1) + dy(a);
        else
            y(a) = sign(y(a-1))*b;
        end
        if abs(z(a-1)) <= b
            z(a) = z(a-1) + dz(a);
        else
            z(a) = sign(z(a-1))*b;
        end
        if (x(a) == agg(1,a-1) + 1)||(x(a) == agg(1,a-1) - 1)
            x(a:n) = x(a);
            y(a:n) = y(a);
            z(a:n) = z(a);
            agg(1,a) = x(a);
            agg(2,a) = y(a);
            agg(3,a) = z(a);
            stuck = 1;
        end
        if (y(a) == agg(2,a-1) + 1)||(y(a) == agg(2,a-1) - 1)
            x(a:n) = x(a);
            y(a:n) = y(a);
            z(a:n) = z(a);
            agg(1,a) = x(a);
            agg(2,a) = y(a);
            agg(3,a) = z(a);
            stuck = 1;
        end
        if (z(a) == agg(3,a-1) + 1)||(z(a) == agg(3,a-1) - 1)
            x(a:n) = x(a);
            y(a:n) = y(a);
            z(a:n) = z(a);
            agg(1,a) = x(a);
            agg(2,a) = y(a);
            agg(3,a) = z(a);
            stuck = 1;        
        end

     end
end

    x(n) = x(n-1);
    y(n) = y(n-1);
    z(n) = z(n-1);

    return