Get_Signature.m

function desc = Get_Signature(PHI, E,DescriptorType,DATASET)

% PHI - eigenfunctions
% E   - eigenvalues

% DescriptorType - specified descriptor to compute 
% DATASET        - specified dataset to load the associated paramemters

% Output: desc - spectral descriptor 


[num_vertices,n_eigenvalues] = size(PHI);

% Step 1. load parameters for the given dataset
switch DATASET
    case 'SHREC2011_Nonrigid'
        PARAMETERS_SS_shrec2011_nonrigid;  
    case 'PARAMETERS_test'
        PARAMETERS_test;          
end
        
% Step 2. compute the spectral descriptors
switch DescriptorType
    
    case 'GPS'
        desc =  PHI(:,start_eval:end_eval)./repmat((sqrt(E(:,start_eval:end_eval))+eps),num_vertices,1);
         
    case 'HKS'
        ee = t0*alpha1.^tau;
        NumTau = length(tau);    

        HKS=zeros(num_vertices,NumTau);

        for ii = 1:NumTau
            HKS(:,ii) = sum(PHI.^2.*...
                repmat( exp(-(ee(ii).*E')),num_vertices,1),2);
        end
        desc =  HKS;
    
    case 'SIHKS'
        HKS=zeros(num_vertices,TimeScale);    
        t = t0*alpha1.^tau;
        for ii = 1:length(tau)
             HKS(:,ii) = sum( -log(alpha1).*PHI.^2.*repmat( (t(ii).*E').*exp(-(t(ii).*E')),num_vertices,1),2) ...
             ./sum(PHI.^2.*repmat( exp(-(t(ii).*E')),num_vertices,1),2);
        end

        SHKS = zeros(num_vertices,(length(tau)-1));
        for ii = 1:(length(tau)-1)
            SHKS(:,ii) = HKS(:,(ii+1))-HKS(:,(ii));
        end

        SIHKS = zeros(num_vertices,(length(tau)-1));
        for ii = 1:num_vertices
            SIHKS(ii,:) = abs(fft(SHKS(ii,:)));
        end
        desc =  SIHKS(:,1:numF);
    
    case 'WKS'
        WKS=zeros(num_vertices,N);

        log_E=log(max(abs(E),1e-6))';
        e=linspace(log_E(2),(max(log_E))/1.02,N);  
        sigma=(e(2)-e(1))*wks_variance;

        C = zeros(1,N); %weights used for the normalization of f_E

        for ii = 1:N
            WKS(:,ii) = sum(PHI.^2.*...
            repmat( exp((-(e(ii) - log_E).^2) ./ (2*sigma.^2)),num_vertices,1),2);
            C(ii) = sum(exp((-(e(ii)-log_E).^2)/(2*sigma.^2)));
        end
        desc =  WKS;   
    
    case 'SGWS'
        MWaveletS = [];
        for nscales = 1:Nscales 
            lmax =  E(n_eigenvalues);
            [g,t]=sgwt_filter_design(lmax,nscales,'designtype',designtype);
            arange=[0 lmax];
            J=numel(g);

            WaveletS = zeros(num_vertices,J);
            for j=1:J
                for ii = 1:n_eigenvalues
                    WaveletS(:,j) = WaveletS(:,j)+...
                     PHI(:,ii).^2.*repmat( g{j}(E(ii)),num_vertices,1);
                end
            end
            MWaveletS = [MWaveletS,WaveletS];
        end
        desc =  MWaveletS;
end

end