Home > chronux_1_15 > 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. 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
           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. Defaults to 0.
0016 %                       e.g. For N = 500, if PAD = 0, we pad the FFT
0017 %                       to 512 points; if PAD = 2, we pad the FFT
0018 %                       to 2048 points, etc.
0019 %           Fs   (sampling frequency) - optional. Default 1.
0020 %           fpass    (frequency band to be used in the calculation in the form
0021 %                                   [fmin fmax])- optional.
0022 %                                   Default all frequencies between 0 and Fs/2
0023 %           err  (error calculation [1 p] - Theoretical error bars; [2 p] - Jackknife error bars
0024 %                                   [0 p] or 0 - no error bars) - optional. Default 0.
0025 %           trialave - not used
0026 %       segave - optional 0 for don't average over segments, 1 for average - default
0027 %       1
0028 % Output:
0029 %       S       (spectrum in form frequency x segments if segave=0; in the form frequency if segave=1)
0030 %       f       (frequencies)
0031 %       varS    (variance of the log spectrum)
0032 %       C       (covariance matrix of the log spectrum - frequency x
0033 %       frequency matrix)
0034 %       Serr    (error bars) only for err(1)>=1
0035 
0036 if nargin < 2; error('Need data and segment information'); end;
0037 if size(data,2)~=1; error('works for only univariate time series'); end;
0038 if nargin < 3 ; params=[]; end;
0039 if nargin < 4 || isempty(segave); segave=1; end;
0040 [tapers,pad,Fs,fpass,err,trialave,params]=getparams(params); clear trialave params
0041 if nargout==4 && err(1)==0; 
0042 %   Errors can't be computed if err(1)=0. Need to change params and run again.
0043     error('When Serr is desired, err(1) has to be non-zero.');
0044 end;
0045 data=change_row_to_column(data);
0046 N=size(data,1); % length of segmented data
0047 dt=1/Fs; % sampling interval
0048 T=N*dt; % length of data in seconds
0049 E=0:win:T-win; % fictitious event triggers
0050 win=[0 win]; % use window length to define left and right limits of windows around triggers
0051 data=createdatamatc(data,E,Fs,win); % segmented data
0052 N=size(data,1); % length of segmented data
0053 nfft=2^(nextpow2(N)+pad);
0054 [f,findx]=getfgrid(Fs,nfft,fpass); 
0055 tapers=dpsschk(tapers,N,Fs); % check tapers
0056 J=mtfftc(data,tapers,nfft,Fs); % compute tapered fourier transforms
0057 J=J(findx,:,:); % restrict to specified frequencies
0058 S=squeeze(mean(conj(J).*J,2)); % spectra of non-overlapping segments (average over tapers)
0059 lS=log(S); % log spectrum for non-overlapping segments
0060 C=cov(lS'); % covariance matrix of the log spectrum
0061 varS=diag(C); % variance of the log spectrum as a function of frequency
0062 if segave==1; S=squeeze(mean(S,2)); end; % mean of the spectrum averaged across segments
0063 if nargout==5; 
0064    Serr=specerr(S,J,err,1);
0065 end;

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