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- function [dS,f]=mtdspectrumpt(data,phi,params,t)
- % 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 one of the following
- % forms:
- % (1) A numeric vector [TW K] where TW is the
- % time-bandwidth product and K is the number of
- % tapers to be used (less than or equal to
- % 2TW-1).
- % (2) A numeric vector [W T p] where W is the
- % bandwidth, T is the duration of the data and p
- % is an integer such that 2TW-p tapers are used. In
- % this form there is no default i.e. to specify
- % the bandwidth, you have to specify T and p as
- % well. Note that the units of W and T have to be
- % consistent: if W is in Hz, T must be in seconds
- % and vice versa. Note that these units must also
- % be consistent with the units of params.Fs: W can
- % be in Hz if and only if params.Fs is in Hz.
- % The default is to use form 1 with TW=3 and K=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
- % 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)
- if nargin < 2; error('Need data and angle'); end;
- if nargin < 3; params=[]; end;
- [tapers,pad,Fs,fpass,err,trialave,params]=getparams(params);
- clear err params
- data=change_row_to_column(data);
- dt=1/Fs; % sampling time
- if nargin < 4;
- [mintime,maxtime]=minmaxsptimes(data);
- t=mintime:dt:maxtime+dt; % time grid for prolates
- end;
- N=length(t); % number of points in grid for dpss
- nfft=max(2^(nextpow2(N)+pad),N); % number of points in fft of prolates
- [f,findx]=getfgrid(Fs,nfft,fpass); % get frequency grid for evaluation
- tapers=dpsschk(tapers,N,Fs); % check tapers
- K=size(tapers,2);
- J=mtfftpt(data,tapers,nfft,t,f,findx); % mt fft for point process times
- A=sqrt(1:K-1);
- A=repmat(A,[size(J,1) 1]);
- A=repmat(A,[1 1 size(J,3)]);
- S=squeeze(mean(J(:,1:K-1,:).*A.*conj(J(:,2:K,:)),2));
- if trialave; S=squeeze(mean(S,2));end;
- nphi=length(phi);
- for p=1:nphi;
- dS(p,:,:)=real(exp(i*phi(p))*S);
- end;
- dS=squeeze(dS);
- dS=change_row_to_column(dS);
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