Homec4science
Diffusion iCAPs public version 2 (master) Browse

iCAPs_v2/packages/gspbox/utils/gsp_check_connectivity_undirected.m
e5f5005bb2efmaster

Last Change
Raw File

gsp_check_connectivity_undirected.m
View Options

function [ bool, in ] = gsp_check_connectivity_undirected( G,param )
%GSP_CHECK_CONNECTIVITY_UNDIRECTED Check if the graph G is aperiodic strongly connected
% Usage: bool = gsp_check_connectivity_undirected( G );
% bool = gsp_check_connectivity_undirected( L );
% bool = gsp_check_connectivity_undirected( W );
% [bool,in]=gsp_check_connectivity_undirected( ... );
%
% Input parameters:
% G,W,L: Graph, Laplacian matrix or Weight martrix
% param: Optional parameters
%
% Output parameters
% bool: Boolean
% in : Nodes without any in connections
%
% Test if each node have at least one in connection and one out
% connection. If this simple test give good results, the function compute
% the perron vector of G and test it. It might take some time.
%
% param is an optional structure that contains the following field
%
% param.verbose*: display parameter - 0 no log - 1 display the errors
%
%
% Url: http://lts2research.epfl.ch/gsp/doc/utils/gsp_check_connectivity_undirected.php
% Copyright (C) 2013-2016 Nathanael Perraudin, Johan Paratte, David I Shuman.
% This file is part of GSPbox version 0.7.0
%
% This program is free software: you can redistribute it and/or modify
% it under the terms of the GNU General Public License as published by
% the Free Software Foundation, either version 3 of the License, or
% (at your option) any later version.
%
% This program is distributed in the hope that it will be useful,
% but WITHOUT ANY WARRANTY; without even the implied warranty of
% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
% GNU General Public License for more details.
%
% You should have received a copy of the GNU General Public License
% along with this program. If not, see <http://www.gnu.org/licenses/>.
% If you use this toolbox please kindly cite
% N. Perraudin, J. Paratte, D. Shuman, V. Kalofolias, P. Vandergheynst,
% and D. K. Hammond. GSPBOX: A toolbox for signal processing on graphs.
% ArXiv e-prints, Aug. 2014.
% http://arxiv.org/abs/1408.5781
%TODO: Make this function better
% Date: 6 june 2013
% Author: Nathanael Perraudin
% Handle Input parameters
if nargin<1, error('Not enought inputs parameters!'); end
if nargin<2, param=struct; end
if ~isfield(param, 'verbose'), param.verbose = 0; end
if isstruct(G)
A=G.W;
else
A=G;
end
% Remove the diagonal
A=A-diag(diag(A));
% Check the connecivity -- simple
bool=~boolean((sum(1.-(sum(A,1)>0))+sum(1.-(sum(A,2)>0))));
in=find(1.-(sum(A,1)>0));
try
if bool
d=bfs(A,1);
bool=~any(d==-1);
end
catch
warning('Using old slow method, install gaimc for speed gain')
if bool
D=diag(sum(A).^(-0.5));
A=D*A*D; % eigenvalues of A between -1 and 1
% We need to check the number of 1 eigenvalues
max_eig_P = eigs(speye(size(A))+A,2);
if abs(max_eig_P(2)-2)<10e-12
if param.verbose
fprintf(' --- the second eigenvalue is 0 ---\n');
end
bool=0;
end
end
if param.verbose
fprintf(' --- End of tests ---\n');
if bool
fprintf(' The graph is connected.\n')
else
fprintf(' The graph is not connected.\n');
end
end
end
end
c4science · Help