function [pooled_mat, card_vec] = pool_config_multi( code_mat, ind_vec, M, Method )
%% POOL_CONFIG_MULTI: pool multi-channels in configuration space;
%==========================================================================
% Input_Args:
% <code_mat> ~ [ N, K ];
% <ind_vec> ~ [ N, 1 ];
% <M>: the number of channels;
% <Method>: 'sum', 'ave', 'max';
%
% Output_Args:
% <pooled_mat> ~ [ M, K ];
% <card_vec> ~ [ M, 1 ];
%
% Cross-Reference Information:
% Called by [doFeatPooling];
% [doFeatPoolingForPoolDimReduct]
% Calling: NULL;
%
%==========================================================================
% modified on 2012/4/17 by Jun Zhu and Weijia Zou;
% For any question, please contact: junnyzhu@sjtu.edu.cn or zouweijia@sjtu.edu.cn
%%
N = size(code_mat,1);
K = size(code_mat,2);
if isempty(code_mat)
pooled_mat = zeros( [M,K] );
card_vec = zeros( [M,1] );
return;
end
switch Method
case 'sum'
[ pooled_mat, card_vec ] = sum_pooling_multi( code_mat, ind_vec, K, M );
case 'ave'
[ pooled_mat, card_vec ] = ave_pooling_multi( code_mat, ind_vec, K, M );
case 'max'
[ pooled_mat, card_vec ] = max_pooling_multi( code_mat, ind_vec, K, M );
otherwise
error('Unknown method on feature pooling;\n');
end
if sum(card_vec) ~= N
error('The number of pooled patches does not match;\n');
end
end % end of function;
%% for 'sum' pooling
function [ pooled_mat, card_vec ] = sum_pooling_multi( code_mat, ind_vec, K, M )
pooled_mat = zeros( [M,K] );
card_vec = zeros( [M,1] );
for i = 1: M
indices_found = find( ind_vec == i );
if isempty(indices_found)
continue;
end
pooled_mat(i,:) = sum( code_mat( indices_found, : ), 1 );
card_vec(i) = length( indices_found );
end % i;
end % end of function;
%% for 'ave' pooling
function [ pooled_mat, card_vec ] = ave_pooling_multi( code_mat, ind_vec, K, M )
pooled_mat = zeros( [M,K] );
card_vec = zeros( [M,1] );
for i = 1: M
indices_found = find( ind_vec == i );
if isempty(indices_found)
continue;
end
pooled_mat(i,:) = mean( code_mat( indices_found, : ), 1 );
card_vec(i) = length( indices_found );
end % i;
end % end of function;
%% for 'max' pooling
function [ pooled_mat, card_vec ] = max_pooling_multi( code_mat, ind_vec, K, M )
pooled_mat = zeros( [M,K] );
card_vec = zeros( [M,1] );
for i = 1: M
indices_found = find( ind_vec == i );
if isempty(indices_found)
continue;
end
pooled_mat(i,:) = max( code_mat( indices_found, : ), [], 1 );
card_vec(i) = length( indices_found );
end % i;
end % end of function;
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