function [mmin, mmax]=plot_ntwk(node_positions, user_positions, plotpitch, min_node_spacing)

%%%%%%%%%%%%%%%%BUGS
%
%  with a circular node layout, I get negative plot locations with more than ~17 nodes
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

Nodes=length(node_positions);
if(size(user_positions,2) == 1);
    Users=0
else
    Users=size(user_positions,1);
end

span=floor(.025*plotpitch);
span_i=floor(.5*span);

xnmin=min(node_positions(:,1));
xnmax=max(node_positions(:,1));
ynmin=min(node_positions(:,2));
ynmax=max(node_positions(:,2));

if(Users >0)
    xumin=min(user_positions(:,1));
    xumax=max(user_positions(:,1));
    yumin=min(user_positions(:,2));
    yumax=max(user_positions(:,2));
else
    xumin=xnmin;
    xumax=xnmax;
    yumin=ynmin;
    yumax=ynmax;
end

xmin=min(xnmin, xumin);
ymin=min(ynmin, yumin);
xmax=max(xnmax, xumax);
ymax=max(ynmax, yumax);

xymin=min(xmin,ymin)-30*min_node_spacing*span/plotpitch;
xymax=max(xmax, ymax)+30*min_node_spacing*span/plotpitch;

x=(xymin:(xymax-xymin)/(plotpitch-1):xymax);
y=(xymin:(xymax-xymin)/(plotpitch-1):xymax);


Z=-1000*ones(plotpitch,plotpitch);

C=-10*ones(plotpitch,plotpitch);

for i=1:Nodes
    for k=-span:span
        mlimit=floor(sqrt(span^2-k^2));  %approximate a circle.  looks cleaner than a square
        for m=-mlimit:mlimit
            npx=floor((plotpitch-1)*(node_positions(i,1)-xymin)/(xymax-xymin)+.5);
            npy=floor((plotpitch-1)*(node_positions(i,2)-xymin)/(xymax-xymin)+.5);
            if(k^2 + m^2 < .7*span^2)
                C(k+1+npx,m+1+npy)=-3;
            else
                C(k+1+npx,m+1+npy)=-20;
            end
            Z(k+1+npx,m+1+npy)=0;
        end
    end
end

if(Users >0)
    for i=1:Users
        for k=-span_i:span_i
            for m=-span_i:span_i
                ipx=floor((plotpitch-1)*(user_positions(i,1)-xymin)/(xymax-xymin)+.5);
                ipy=floor((plotpitch-1)*(user_positions(i,2)-xymin)/(xymax-xymin)+.5);
                C(1+m+ipx,1+k+ipy)=5;
                Z(1+m+ipx,1+k+ipy)=-5;
            end
        end
    end
end

gcf=figure(30);
surf(x,y,Z',C');
shading interp
colormap(jet)
grid on

% symmetrical axis around (0,0)
mmax=1.2*max(max(abs(xmin),abs(ymin)),max(abs(xmax),abs(ymax)));
mmin=-mmax;
axis([mmin mmax mmin mmax -5 5]);
axis square
axis xy
caxis([-10 0])
view(2)
set(gcf,'NumberTitle','off','Name','Node Plot')
xlabel('X');
ylabel('Y');