Home > chronux_1_1 > pointtimes > mtdspectrumpt.m

mtdspectrumpt

PURPOSE ^

Multi-taper spectral derivative - point process times

SYNOPSIS ^

function [dS,f]=mtdspectrumpt(data,phi,params,t)

DESCRIPTION ^

 Multi-taper spectral derivative - point process times

 Usage:

 [dS,f]=mtdspectrumpt(data,phi,params,t)
 Input: 
   Note that all times can be in arbitrary units. But the units have to be
   consistent. So, if E is in secs, win, t have to be in secs, and Fs has to
   be Hz. If E is in samples, so are win and t, and Fs=1. In case of spike
   times, the units have to be consistent with the units of data as well.
       data        (structure array of spike times with dimension channels/trials; also accepts 1d array of spike times) -- required
       phi         (angle for evaluation of derivative) -- required.
                       e.g. phi=[0,pi/2] giving the time and frequency derivatives
       params: structure with fields tapers, pad, Fs, fpass, 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
           trialave (average over trials when 1, don't average when 0) -
           optional. Default 0
       t        (time grid over which the tapers are to be calculated:
                      this argument is useful when calling the spectrum
                      calculation routine from a moving window spectrogram
                      calculation routine). If left empty, the spike times
                      are used to define the grid.
 Output:
       dS      (spectral derivative in form phi x frequency x channels/trials if trialave=0; function of phi x frequency if trialave=1)
       f       (frequencies)

CROSS-REFERENCE INFORMATION ^

This function calls: This function is called by:

SOURCE CODE ^

0001 function [dS,f]=mtdspectrumpt(data,phi,params,t)
0002 % Multi-taper spectral derivative - point process times
0003 %
0004 % Usage:
0005 %
0006 % [dS,f]=mtdspectrumpt(data,phi,params,t)
0007 % Input:
0008 %   Note that all times can be in arbitrary units. But the units have to be
0009 %   consistent. So, if E is in secs, win, t have to be in secs, and Fs has to
0010 %   be Hz. If E is in samples, so are win and t, and Fs=1. In case of spike
0011 %   times, the units have to be consistent with the units of data as well.
0012 %       data        (structure array of spike times with dimension channels/trials; also accepts 1d array of spike times) -- required
0013 %       phi         (angle for evaluation of derivative) -- required.
0014 %                       e.g. phi=[0,pi/2] giving the time and frequency derivatives
0015 %       params: structure with fields tapers, pad, Fs, fpass, trialave
0016 %       -optional
0017 %           tapers (precalculated tapers from dpss, or in the form [NW K] e.g [3 5]) -- optional. If not
0018 %                                                 specified, use [NW K]=[3 5]
0019 %            pad            (padding factor for the FFT) - optional. Defaults to 0.
0020 %                       e.g. For N = 500, if PAD = 0, we pad the FFT
0021 %                       to 512 points; if PAD = 2, we pad the FFT
0022 %                       to 2048 points, etc.
0023 %           Fs   (sampling frequency) - optional. Default 1.
0024 %           fpass    (frequency band to be used in the calculation in the form
0025 %                                   [fmin fmax])- optional.
0026 %                                   Default all frequencies between 0 and Fs/2
0027 %           trialave (average over trials when 1, don't average when 0) -
0028 %           optional. Default 0
0029 %       t        (time grid over which the tapers are to be calculated:
0030 %                      this argument is useful when calling the spectrum
0031 %                      calculation routine from a moving window spectrogram
0032 %                      calculation routine). If left empty, the spike times
0033 %                      are used to define the grid.
0034 % Output:
0035 %       dS      (spectral derivative in form phi x frequency x channels/trials if trialave=0; function of phi x frequency if trialave=1)
0036 %       f       (frequencies)
0037 if nargin < 2; error('Need data and angle'); end;
0038 if nargin < 3; params=[]; end;
0039 [tapers,pad,Fs,fpass,err,trialave,params]=getparams(params);
0040 clear err params
0041 data=change_row_to_column(data);
0042 dt=1/Fs; % sampling time
0043 if nargin < 4;
0044    [mintime,maxtime]=minmaxsptimes(data);
0045    t=mintime:dt:maxtime+dt; % time grid for prolates
0046 end;
0047 N=length(t); % number of points in grid for dpss
0048 nfft=2^(nextpow2(N)+pad); % number of points in fft of prolates
0049 [f,findx]=getfgrid(Fs,nfft,fpass); % get frequency grid for evaluation
0050 tapers=dpsschk(tapers,N,Fs); % check tapers
0051 K=size(tapers,2);
0052 J=mtfftpt(data,tapers,nfft,Fs,t,f,findx); % mt fft for point process times
0053 A=sqrt(1:K-1);
0054 A=repmat(A,[size(J,1) 1]);
0055 A=repmat(A,[1 1 size(J,3)]);
0056 S=squeeze(mean(J(:,1:K-1,:).*A.*conj(J(:,2:K,:)),2));
0057 if trialave; S=squeeze(mean(S,2));end;
0058 nphi=length(phi);
0059 for p=1:nphi;
0060     dS(p,:,:)=real(exp(i*phi(p))*S);
0061 end;
0062 dS=squeeze(dS);
0063 dS=change_row_to_column(dS);

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