crossspecpt

PURPOSE ^

Multi-taper cross-spectrum - point process given as times

SYNOPSIS ^

function [S12,f]=crossspecpt(data1,data2,tapers,pad,Fs,fpass)

DESCRIPTION ^

 Multi-taper cross-spectrum - point process given as times

 Usage:

 [S12,f]=crossspecpt(data1,data2,tapers,pad,Fs,fpass)
 Input: 
       data1  (structure array of channels/trials with spike times; also accepts 1d column vector of times) -- required
       data2  (structure array of channels/trials with spike times; also accepts 1d column vector of times) -- required
       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          (binning frequency for fft grid used to calculate fft of prolates. 1/Fs is the time between consecutive
                                   points on the grid used for evaluation
                                   of the prolates) - 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
 Output:
       S12 (cross spectrum frequency index x channels/trials)
       f (frequencies)

CROSS-REFERENCE INFORMATION ^

This function calls: This function is called by:

SOURCE CODE ^

0001 function [S12,f]=crossspecpt(data1,data2,tapers,pad,Fs,fpass)
0002 % Multi-taper cross-spectrum - point process given as times
0003 %
0004 % Usage:
0005 %
0006 % [S12,f]=crossspecpt(data1,data2,tapers,pad,Fs,fpass)
0007 % Input:
0008 %       data1  (structure array of channels/trials with spike times; also accepts 1d column vector of times) -- required
0009 %       data2  (structure array of channels/trials with spike times; also accepts 1d column vector of times) -- required
0010 %       tapers (precalculated tapers from dpss, or in the form [NW K] e.g [3 5]) -- optional. If not
0011 %                                                 specified, use [NW K]=[3 5]
0012 %        pad            (padding factor for the FFT) - optional. Defaults to 0.
0013 %                       e.g. For N = 500, if PAD = 0, we pad the FFT
0014 %                       to 512 points; if PAD = 2, we pad the FFT
0015 %                       to 2048 points, etc.
0016 %       Fs          (binning frequency for fft grid used to calculate fft of prolates. 1/Fs is the time between consecutive
0017 %                                   points on the grid used for evaluation
0018 %                                   of the prolates) - optional. Default 1.
0019 %       fpass    (frequency band to be used in the calculation in the form
0020 %                                   [fmin fmax])- optional.
0021 %                                   Default all frequencies between 0 and Fs/2
0022 % Output:
0023 %       S12 (cross spectrum frequency index x channels/trials)
0024 %       f (frequencies)
0025 if nargin < 2; error('Need data1 and data2'); end;
0026 if nargin < 3; tapers=[3 5];end;
0027 if nargin < 4; pad=0;end;
0028 if nargin < 5; Fs=1; end;
0029 if nargin < 6; fpass=[0 Fs/2]; end;
0030 
0031 if isempty(tapers); tapers=[3 5]; end;
0032 if isempty(pad);pad=0;end;
0033 if isempty(Fs); Fs=1; end;
0034 if isempty(fpass); fpass=[0 Fs/2]; end;
0035 
0036 [mintime1,maxtime1]=minmaxsptimes(data1);
0037 [mintime2,maxtime2]=minmaxsptimes(data2);
0038 mintime=min(mintime1,mintime2);
0039 maxtime=max(maxtime1,maxtime2);
0040 dt=1/Fs;
0041 t=mintime:dt:maxtime+dt; % time grid for prolates
0042 N=length(t); % number of points in grid for dpss
0043 nfft=2^(nextpow2(N)+pad); % number of points in fft of prolates
0044 [f,findx]=getfgrid(Fs,nfft,fpass); 
0045 tapers=dpsschk(tapers,N,Fs); % check tapers
0046 [J1,Msp1,Nsp1]=mtfftpt(data1,tapers,nfft,Fs,t,f,findx);
0047 [J2,Msp2,Nsp2]=mtfftpt(data2,tapers,nfft,Fs,t,f,findx);
0048 J1=J1(findx,:,:); J2=J2(findx,:,:);
0049 S12=squeeze(mean(conj(J1).*J2,2));
0050 if trialave; S12=squeeze(mean(S12,2));end;

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