Home > chronux_1_50 > continuous > mtspectrumsegc.m

mtspectrumsegc

PURPOSE ^

Multi-taper segmented spectrum for a univariate continuous process

SYNOPSIS ^

function [S,f,varS,C,Serr]=mtspectrumsegc(data,win,params,segave)

DESCRIPTION ^

 Multi-taper segmented spectrum for a univariate continuous process

 Usage:

 [S,f,varS,C,Serr]=mtspectrumsegc(data,win,params,segave)
 Input: 
 Note units have to be consistent. See chronux.m for more information.
       data (single channel) -- required
       win  (duration of the segments) - required. 
       params: structure with fields tapers, pad, Fs, fpass, err, trialave
       - 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 (can take values -1,0,1,2...). 
                    -1 corresponds to no padding, 0 corresponds to padding
                    to the next highest power of 2 etc.
                       e.g. For N = 500, if PAD = -1, we do not pad; if PAD = 0, we pad the FFT
                       to 512 points, if pad=1, we pad to 1024 points etc.
                       Defaults to 0.
           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
           err  (error calculation [1 p] - Theoretical error bars; [2 p] - Jackknife error bars
                                   [0 p] or 0 - no error bars) - optional. Default 0.
           trialave - not used
       segave - optional 0 for don't average over segments, 1 for average - default
       1
 Output:
       S       (spectrum in form frequency x segments if segave=0; in the form frequency if segave=1)
       f       (frequencies)
       varS    (variance of the log spectrum)
       C       (covariance matrix of the log spectrum - frequency x
       frequency matrix)
       Serr    (error bars) only for err(1)>=1

CROSS-REFERENCE INFORMATION ^

This function calls: This function is called by:

SOURCE CODE ^

0001 function [S,f,varS,C,Serr]=mtspectrumsegc(data,win,params,segave)
0002 % Multi-taper segmented spectrum for a univariate continuous process
0003 %
0004 % Usage:
0005 %
0006 % [S,f,varS,C,Serr]=mtspectrumsegc(data,win,params,segave)
0007 % Input:
0008 % Note units have to be consistent. See chronux.m for more information.
0009 %       data (single channel) -- required
0010 %       win  (duration of the segments) - required.
0011 %       params: structure with fields tapers, pad, Fs, fpass, err, trialave
0012 %       - optional
0013 %           tapers (precalculated tapers from dpss, or in the form [NW K] e.g [3 5]) -- optional. If not
0014 %                                                 specified, use [NW K]=[3 5]
0015 %            pad            (padding factor for the FFT) - optional (can take values -1,0,1,2...).
0016 %                    -1 corresponds to no padding, 0 corresponds to padding
0017 %                    to the next highest power of 2 etc.
0018 %                       e.g. For N = 500, if PAD = -1, we do not pad; if PAD = 0, we pad the FFT
0019 %                       to 512 points, if pad=1, we pad to 1024 points etc.
0020 %                       Defaults to 0.
0021 %           Fs   (sampling frequency) - optional. Default 1.
0022 %           fpass    (frequency band to be used in the calculation in the form
0023 %                                   [fmin fmax])- optional.
0024 %                                   Default all frequencies between 0 and Fs/2
0025 %           err  (error calculation [1 p] - Theoretical error bars; [2 p] - Jackknife error bars
0026 %                                   [0 p] or 0 - no error bars) - optional. Default 0.
0027 %           trialave - not used
0028 %       segave - optional 0 for don't average over segments, 1 for average - default
0029 %       1
0030 % Output:
0031 %       S       (spectrum in form frequency x segments if segave=0; in the form frequency if segave=1)
0032 %       f       (frequencies)
0033 %       varS    (variance of the log spectrum)
0034 %       C       (covariance matrix of the log spectrum - frequency x
0035 %       frequency matrix)
0036 %       Serr    (error bars) only for err(1)>=1
0037 
0038 if nargin < 2; error('Need data and segment information'); end;
0039 data=change_row_to_column(data);
0040 if size(data,2)~=1; error('works for only univariate time series'); end;
0041 if nargin < 3 ; params=[]; end;
0042 if nargin < 4 || isempty(segave); segave=1; end;
0043 [tapers,pad,Fs,fpass,err,trialave,params]=getparams(params); clear trialave params
0044 if nargout==4 && err(1)==0; 
0045 %   Errors can't be computed if err(1)=0. Need to change params and run again.
0046     error('When Serr is desired, err(1) has to be non-zero.');
0047 end;
0048 N=size(data,1); % length of segmented data
0049 dt=1/Fs; % sampling interval
0050 T=N*dt; % length of data in seconds
0051 E=0:win:T-win; % fictitious event triggers
0052 win=[0 win]; % use window length to define left and right limits of windows around triggers
0053 data=createdatamatc(data,E,Fs,win); % segmented data
0054 N=size(data,1); % length of segmented data
0055 nfft=max(2^(nextpow2(N)+pad),N);
0056 [f,findx]=getfgrid(Fs,nfft,fpass); 
0057 tapers=dpsschk(tapers,N,Fs); % check tapers
0058 J=mtfftc(data,tapers,nfft,Fs); % compute tapered fourier transforms
0059 J=J(findx,:,:); % restrict to specified frequencies
0060 S=squeeze(mean(conj(J).*J,2)); % spectra of non-overlapping segments (average over tapers)
0061 if segave==1; SS=squeeze(mean(S,2)); else; SS=S;end; % mean of the spectrum averaged across segments
0062 if nargout > 2
0063     lS=log(S); % log spectrum for nonoverlapping segments
0064     varS=var(lS',1)'; % variance of log spectrum
0065 %     varS=var(lS',1)';% variance of the log spectrum R13
0066     if nargout > 3
0067        C=cov(lS'); % covariance matrix of the log spectrum
0068        if nargout==5; 
0069           Serr=specerr(SS,J,err,segave);
0070        end;
0071     end;
0072 end;
0073 S=SS;

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