Home > chronux > spectral_analysis > 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 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...).
to the next highest power of 2 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)```

## CROSS-REFERENCE INFORMATION This function calls:
• minmaxsptimes Find the minimum and maximum of the spike times in each channel
• mtfftpt Multi-taper fourier transform for point process given as times
This function is called by:
• mtdspecgrampt Multi-taper derivative time-frequency spectrum - point process times

## 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;
0013 %                   also accepts 1d array of spike times) -- required
0014 %       phi         (angle for evaluation of derivative) -- required.
0015 %                       e.g. phi=[0,pi/2] giving the time and frequency derivatives
0016 %       params: structure with fields tapers, pad, Fs, fpass, trialave
0017 %       -optional
0018 %           tapers : precalculated tapers from dpss or in the one of the following
0019 %                    forms:
0020 %                   (1) A numeric vector [TW K] where TW is the
0021 %                       time-bandwidth product and K is the number of
0022 %                       tapers to be used (less than or equal to
0023 %                       2TW-1).
0024 %                   (2) A numeric vector [W T p] where W is the
0025 %                       bandwidth, T is the duration of the data and p
0026 %                       is an integer such that 2TW-p tapers are used. In
0027 %                       this form there is no default i.e. to specify
0028 %                       the bandwidth, you have to specify T and p as
0029 %                       well. Note that the units of W and T have to be
0030 %                       consistent: if W is in Hz, T must be in seconds
0031 %                       and vice versa. Note that these units must also
0032 %                       be consistent with the units of params.Fs: W can
0033 %                       be in Hz if and only if params.Fs is in Hz.
0034 %                       The default is to use form 1 with TW=3 and K=5
0035 %
0036 %            pad            (padding factor for the FFT) - optional (can take values -1,0,1,2...).
0038 %                    to the next highest power of 2 etc.
0039 %                       e.g. For N = 500, if PAD = -1, we do not pad; if PAD = 0, we pad the FFT
0040 %                       to 512 points, if pad=1, we pad to 1024 points etc.
0041 %                       Defaults to 0.
0042 %           Fs   (sampling frequency) - optional. Default 1.
0043 %           fpass    (frequency band to be used in the calculation in the form
0044 %                                   [fmin fmax])- optional.
0045 %                                   Default all frequencies between 0 and Fs/2
0046 %           trialave (average over trials when 1, don't average when 0) -
0047 %           optional. Default 0
0048 %       t        (time grid over which the tapers are to be calculated:
0049 %                      this argument is useful when calling the spectrum
0050 %                      calculation routine from a moving window spectrogram
0051 %                      calculation routine). If left empty, the spike times
0052 %                      are used to define the grid.
0053 % Output:
0054 %       dS      (spectral derivative in form phi x frequency x channels/trials if trialave=0;
0055 %               function of phi x frequency if trialave=1)
0056 %       f       (frequencies)
0057 if nargin < 2; error('Need data and angle'); end;
0058 if nargin < 3; params=[]; end;
0060 clear err params
0061 data=change_row_to_column(data);
0062 dt=1/Fs; % sampling time
0063 if nargin < 4;
0064    [mintime,maxtime]=minmaxsptimes(data);
0065    t=mintime:dt:maxtime+dt; % time grid for prolates
0066 end;
0067 N=length(t); % number of points in grid for dpss
0068 nfft=max(2^(nextpow2(N)+pad),N); % number of points in fft of prolates
0069 [f,findx]=getfgrid(Fs,nfft,fpass); % get frequency grid for evaluation
0070 tapers=dpsschk(tapers,N,Fs); % check tapers
0071 K=size(tapers,2);
0072 J=mtfftpt(data,tapers,nfft,t,f,findx); % mt fft for point process times
0073 A=sqrt(1:K-1);
0074 A=repmat(A,[size(J,1) 1]);
0075 A=repmat(A,[1 1 size(J,3)]);
0076 S=squeeze(mean(J(:,1:K-1,:).*A.*conj(J(:,2:K,:)),2));
0077 if trialave; S=squeeze(mean(S,2));end;
0078 nphi=length(phi);
0079 for p=1:nphi;
0080     dS(p,:,:)=real(exp(i*phi(p))*S);
0081 end;
0082 dS=squeeze(dS);
0083 dS=change_row_to_column(dS);```

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