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## Copyright (C) 2024 David Legland
## All rights reserved.
##
## Redistribution and use in source and binary forms, with or without
## modification, are permitted provided that the following conditions are met:
##
## 1 Redistributions of source code must retain the above copyright notice,
## this list of conditions and the following disclaimer.
## 2 Redistributions in binary form must reproduce the above copyright
## notice, this list of conditions and the following disclaimer in the
## documentation and/or other materials provided with the distribution.
##
## THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ''AS IS''
## AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
## IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
## ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR
## ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
## DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
## SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
## CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
## OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
## OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
##
## The views and conclusions contained in the software and documentation are
## those of the authors and should not be interpreted as representing official
## policies, either expressed or implied, of the copyright holders.
function [degree, node] = grNodeDegree(node, edges)
%GRNODEDEGREE Degree of a node in a (undirected) graph.
%
% DEGREE = grNodeDegree(NODE_INDEX, EDGES);
% return the degree of a node in the given edge list, that is the number
% of edges connected to it.
% NODE_INDEX is the index of the node, and EDGES is a liste of couples of
% indices (origin and destination node).
% This degree is the sum of inner degree (number of edges arriving on the
% node) and the outer degree (number of emanating edges).
%
% Note: Also works when NODE_INDEX is a vector of indices
%
% DEGREE = grNodeDegree(EDGES);
% Return the degree of each node references by the array EDGES. DEGREE is
% a column vector with as many rows as the number of nodes referenced by
% edges.
%
% [DEG, INDS] = grNodeDegree(EDGES);
% Also returns the indices of the nodes that were referenced.
%
% Example
% edges = [1 2;1 3;2 3;2 4;3 4];
% grNodeDegree(2, edges)
% ans =
% 3
% grNodeDegree(edges)'
% ans =
% 2 3 3 2
%
% See also grNodeInnerDegree, grNodeOuterDegree
%
% ------
% Author: David Legland
% E-mail: david.legland@inrae.fr
% Created: 2003-08-13
% Copyright 2003-2023 INRA - CEPIA Nantes - MIAJ (Jouy-en-Josas)
% If only edge array is given, assume we want the degree of each node
if nargin == 1
edges = node;
node = unique(edges(:));
end
% allocate array for result
degree = zeros(size(node));
% for each node ID, count the number of edges containing it
for i = 1:length(node(:))
degree(i) = sum(edges(:,1) == node(i)) + sum(edges(:,2) == node(i));
end
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