Home > chronux_1_50 > continuous > CrossSpecMatc.m

CrossSpecMatc

PURPOSE ^

Multi-taper cross-spectral matrix - another routine, allows for multiple trials and channels

SYNOPSIS ^

function [Sc,Cmat,Ctot,Cvec,Cent,f]=CrossSpecMatc(data,win,params)

DESCRIPTION ^

 Multi-taper cross-spectral matrix - another routine, allows for multiple trials and channels 
 Does not do confidence intervals. Also this routine always averages over trials - continuous process

 Usage:

 [Sc,Cmat,Ctot,Cvec,Cent,f]=CrossSpecMatc(data,win,params)
 Input: 
 Note units have to be consistent. See chronux.m for more information.
       data (in form samples x channels x trials) 
       win  (duration of non-overlapping window)
       params: structure with fields tapers, pad, Fs, fpass
       - optional
           tapers (precalculated tapers from dpss, or in the form [NW K] e.g [3 5]) -- optional. If not 
                                                 specified, use [NW K]=[3 5]
            pad            (padding factor for the FFT) - optional. Defaults to 0.  
                       e.g. For N = 500, if PAD = 0, we pad the FFT 
                       to 512 points; if PAD = 2, we pad the FFT
                       to 2048 points, etc.
           Fs   (sampling frequency) - optional. Default 1.
           fpass    (frequency band to be used in the calculation in the form
                                   [fmin fmax])- optional. 
                                   Default all frequencies between 0 and Fs/2
 Output:
       Sc (cross spectral matrix frequency x channels x channels)
       Cmat Coherence matrix frequency x channels x channels
       Ctot Total coherence: SV(1)^2/sum(SV^2) (frequency)
       Cvec leading Eigenvector (frequency x channels)
       Cent A different measure of total coherence: GM/AM of SV^2s
       f (frequencies)

CROSS-REFERENCE INFORMATION ^

This function calls: This function is called by:

SOURCE CODE ^

0001 function [Sc,Cmat,Ctot,Cvec,Cent,f]=CrossSpecMatc(data,win,params)
0002 % Multi-taper cross-spectral matrix - another routine, allows for multiple trials and channels
0003 % Does not do confidence intervals. Also this routine always averages over trials - continuous process
0004 %
0005 % Usage:
0006 %
0007 % [Sc,Cmat,Ctot,Cvec,Cent,f]=CrossSpecMatc(data,win,params)
0008 % Input:
0009 % Note units have to be consistent. See chronux.m for more information.
0010 %       data (in form samples x channels x trials)
0011 %       win  (duration of non-overlapping window)
0012 %       params: structure with fields tapers, pad, Fs, fpass
0013 %       - optional
0014 %           tapers (precalculated tapers from dpss, or in the form [NW K] e.g [3 5]) -- optional. If not
0015 %                                                 specified, use [NW K]=[3 5]
0016 %            pad            (padding factor for the FFT) - optional. Defaults to 0.
0017 %                       e.g. For N = 500, if PAD = 0, we pad the FFT
0018 %                       to 512 points; if PAD = 2, we pad the FFT
0019 %                       to 2048 points, etc.
0020 %           Fs   (sampling frequency) - optional. Default 1.
0021 %           fpass    (frequency band to be used in the calculation in the form
0022 %                                   [fmin fmax])- optional.
0023 %                                   Default all frequencies between 0 and Fs/2
0024 % Output:
0025 %       Sc (cross spectral matrix frequency x channels x channels)
0026 %       Cmat Coherence matrix frequency x channels x channels
0027 %       Ctot Total coherence: SV(1)^2/sum(SV^2) (frequency)
0028 %       Cvec leading Eigenvector (frequency x channels)
0029 %       Cent A different measure of total coherence: GM/AM of SV^2s
0030 %       f (frequencies)
0031 d=ndims(data);
0032 if d<2, error('Need multidimensional array'); end
0033 if d==2, [N,C]=size(data); end;
0034 if d==3, [N,C,Ntr]=size(data); end; 
0035 if nargin < 3; params=[]; end;
0036 [tapers,pad,Fs,fpass,err,trialave,params]=getparams(params);
0037 clear err trialave params
0038 nwin=round(win*Fs); nfft=max(2^(nextpow2(nwin)+pad),nwin); 
0039 [f,findx]=getfgrid(Fs,nfft,fpass); 
0040 tapers=dpsschk(tapers,nwin,Fs); % check tapers
0041 Sc=zeros(length(findx),C,C);
0042 
0043 Nwins=floor(N/nwin);
0044 
0045 if d==3, % If there are multiple trials
0046 for iwin=1:Nwins,
0047     for i=1:Ntr, 
0048         data1=squeeze(data(1+(iwin-1)*nwin:iwin*nwin,:,i));
0049         J1=mtfftc(detrend(data1),tapers,nfft,Fs);
0050         J1=J1(findx,:,:);
0051         for k=1:C,
0052             for l=1:C,
0053                 spec=squeeze(mean(conj(J1(:,:,k)).*J1(:,:,l),2)); 
0054             Sc(:,k,l)=Sc(:,k,l)+spec;
0055             end
0056         end
0057     end
0058 end
0059 Sc=Sc/(Nwins*Ntr);
0060 end
0061 
0062 if d==2, % only one trial
0063 for iwin=1:Nwins,
0064         data1=squeeze(data(1+(iwin-1)*nwin:iwin*nwin,:));
0065         J1=mtfftc(data1,tapers,nfft,Fs);
0066         J1=J1(findx,:,:);
0067         for k=1:C,
0068             for l=1:C,
0069             Sc(:,k,l)=Sc(:,k,l)+squeeze(mean(conj(J1(:,:,k)).*J1(:,:,l),2));
0070             end
0071         end
0072 end
0073 Sc=Sc/Nwins;
0074 end
0075 
0076 Cmat=Sc;
0077 Sdiag=zeros(length(findx),C);
0078 for k=1:C,
0079     Sdiag(:,k)=squeeze(Sc(:,k,k));
0080 end
0081 
0082 for k=1:C,
0083     for l=1:C,
0084         Cmat(:,k,l)=Sc(:,k,l)./sqrt(abs(Sdiag(:,k).*Sdiag(:,l)));
0085     end
0086 end
0087 
0088 Ctot=zeros(length(findx),1); Cent=Ctot;
0089 Cvec=zeros(length(findx),C);
0090 for i=1:length(findx),
0091     [u s]=svd(squeeze(Sc(i,:,:)));s=diag(s);
0092     Ctot(i)=s(1).^2/sum(s.^2); Cent(i)=exp(mean(log(s.^2)))/mean(s.^2);             
0093     Cvec(i,:)=transpose(u(:,1));
0094 end
0095

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