function [Xout,Yout,Zout]=gplot3(A,xy,lc)
%GPLOT Plot graph, as in "graph theory".
% Mod from gplot.m by els 12/12/03 for 3D Geometry plot
% GPLOT(A,xy) plots the graph specified by A and xy. A graph, G, is
% a set of nodes numbered from 1 to n, and a set of connections, or
% edges, between them.
%
% In order to plot G, two matrices are needed. The adjacency matrix,
% A, has a(i,j) nonzero if and only if node i is connected to node
% j. The coordinates array, xy, is an n-by-2 matrix with the
% position for node i in the i-th row, xy(i,:) = [x(i) y(i)].
%
% GPLOT(A,xy,LineSpec) uses line type and color specified in the
% string LineSpec. See PLOT for possibilities.
%
% [X,Y] = GPLOT(A,xy) returns the NaN-punctuated vectors
% X and Y without actually generating a plot. These vectors
% can be used to generate the plot at a later time if desired.
%
% See also SPY, TREEPLOT.
% John Gilbert, 1991.
% Modified 1-21-91, LS; 2-28-92, 6-16-92 CBM.
% Copyright 1984-2002 The MathWorks, Inc.
% $Revision: 1.1 $ $Date: 2003/12/12 23:16:51 $
[i,j] = find(A);
[ignore, p] = sort(max(i,j));
i = i(p);
j = j(p);
% Create a long, NaN-separated list of line segments,
% rather than individual segments.
X = [ xy(i,1) xy(j,1) repmat(NaN,size(i))]';
Y = [ xy(i,2) xy(j,2) repmat(NaN,size(i))]';
Z = [ xy(i,3) xy(j,3) repmat(NaN,size(i))]';
X = X(:);
Y = Y(:);
Z = Z(:);
if nargout==0,
if nargin<3,
plot3(X, Y, Z)
else
plot3(X, Y, Z,lc);
end
else
Xout = X;
Yout = Y;
Zout = Z;
end