I am trying to plot a 3D graph, determining the x and y values using an array and the z values using if/else. This is the code I am playing with but I can't get it to work:

xmin=-1000;

xmax=1000;

division=1.0;

num=((xmax-xmin)/division)+1;

for i=1:(num/2);

x(i)=i-(num/2);

for k=1:(num/2);

y(k)=k-(num/2);

for j=1:10:(num/2);

u(j)=j-num/2;

v(j)=j+6-num/2;

if ((x(i)>=u(j))&&(x(i)<=v(j))&&(x(i)<1000)&&(x(i)>0)&&(y(k)>0)&&(y(k)<1000)) |((x(i)>-1000)&&(x(i)<0)&&(y(k)>-1000)&&(y(k)<1000))|((x(i)>0)&&(x(i)<1000)&&(y(k)>-1000)&&(y(k)<0));

z(i,k)=1.0;

else

z(i,k)=0.0;

end

end

end

end

surf(x,y,z)

I am very new to this so any help would be very valuable, thanks!