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iCAPs/packages/gspbox/utils/gsp_jtv_cheby_coeff.m
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gsp_jtv_cheby_coeff.m
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function c = gsp_jtv_cheby_coeff(G, filter, filtertype, m, N,param)
%GSP_JTV_CHEBY_COEFF : Compute Chebyshev coefficients for a time-vertex filterbank
% Usage: c = gsp_jtv_cheby_coeff(G, filter);
% c = gsp_jtv_cheby_coeff(G, filter, m);
% c = gsp_jtv_cheby_coeff(G, filter, m, N);
%
% Input parameters:
% G : Time-Graph structure
% filter : Cell array of time-vertex filters
% filtertype : Filter domain (ts,js,ts-array,js-array)
% m : maximum order Chebyshev coefficient to compute (default 30)
% N : grid order used to compute quadrature (default is m+1)
% param : structure of optional parameter
% Output parameters
% c : matrix of Chebyshev coefficients
%
% Additional parameters
% ---------------------
% param.verbose : Verbosity level (1 display the warning - 0 no log)
% (default 1).
%
% Url: http://lts2research.epfl.ch/gsp/doc/utils/gsp_jtv_cheby_coeff.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
%
% Author: Francesco Grassi
% Date : July 2016
if nargin < 6
param = struct;
end
if ~isfield(param,'verbose'), param.verbose = 1; end;
if nargin < 4
m = 30;
end
if nargin < 5
N = m+1;
end
if isstruct(G)
if or(~isfield(G.jtv,'T'),~isfield(G.jtv,'fs'));
error('GSP_JTV_CHEBY_COEFF need time dimension. Use GSP_JTV_GRAPH.')
end
else
error('Invalid graph structure.')
end
T = G.jtv.T;
if G.jtv.extension
tau = 2*G.jtv.T-1;
else
tau = T;
end
if iscell(filter)
Nf = length(filter);
c = zeros(m+1,tau,Nf);
for ii = 1: Nf
c(:,:,ii) = gsp_jtv_cheby_coeff(G, filter{ii},filtertype, m, N,param);
end
return;
end
if ~isfield(G,'lmax');
G = gsp_estimate_lmax(G);
if param.verbose
warning(['GSP_JTV_CHEBY_COEFF: The variable lmax is not ',...
'available. The function will compute it for you. ',...
'However, if you apply many time this function, you ',...
'should precompute it using the function: ',...
'gsp_estimate_lmax']);
end
end
arange = [0, G.lmax];
a1=(arange(2)-arange(1))/2;
a2=(arange(2)+arange(1))/2;
t = gsp_jtv_ta(G);
c = zeros(N,T);
param.domain = 'joint-spectral';
for ii=1:m+1
c(ii,:) = sum( gsp_jtv_filter_evaluate(filter,filtertype,a1* cos( (pi*((1:N)-0.5))/N) + a2,t,param ) .* ...
repmat(cos( pi*(ii-1)*((1:N)-0.5)/N).',1,T)) *2/N;
end
if G.jtv.extension
c = [c zeros(N,T-1)];
end
end
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