Multi-taper coherency,cross-spectral matrix - continuous process
Usage:
[C,phi,S12,f,confC,phistd,Cerr]=cohmatrixc(data,params)
Input:
Note units have to be consistent. See chronux.m for more information.
data (in form samples x channels) -- required
params: structure with fields tapers, pad, Fs, fpass, err
- 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
err (error calculation [1 p] - Theoretical error bars; [2 p] - Jackknife error bars
[0 p] or 0 - no error bars) - optional. Default 0.
Output:
C (magnitude of coherency frequency x channels x channels)
phi (phase of coherency frequency x channels x channels)
S12 (cross-spectral matrix frequency x channels x channels)
f (frequencies)
confC (confidence level for C at 1-p %) - only for err(1)>=1
phistd - theoretical/jackknife (depending on err(1)=1/err(1)=2) standard deviation for phi
Note that phi + 2 phistd and phi - 2 phistd will give 95% confidence
bands for phi - only for err(1)>=1
Cerr (Jackknife error bars for C - use only for Jackknife - err(1)=2)0001 function [C,phi,S12,f,confC,phistd,Cerr]=cohmatrixc(data,params) 0002 % Multi-taper coherency,cross-spectral matrix - continuous process 0003 % 0004 % Usage: 0005 % 0006 % [C,phi,S12,f,confC,phistd,Cerr]=cohmatrixc(data,params) 0007 % Input: 0008 % Note units have to be consistent. See chronux.m for more information. 0009 % data (in form samples x channels) -- required 0010 % params: structure with fields tapers, pad, Fs, fpass, err 0011 % - optional 0012 % tapers : precalculated tapers from dpss or in the one of the following 0013 % forms: 0014 % (1) A numeric vector [TW K] where TW is the 0015 % time-bandwidth product and K is the number of 0016 % tapers to be used (less than or equal to 0017 % 2TW-1). 0018 % (2) A numeric vector [W T p] where W is the 0019 % bandwidth, T is the duration of the data and p 0020 % is an integer such that 2TW-p tapers are used. In 0021 % this form there is no default i.e. to specify 0022 % the bandwidth, you have to specify T and p as 0023 % well. Note that the units of W and T have to be 0024 % consistent: if W is in Hz, T must be in seconds 0025 % and vice versa. Note that these units must also 0026 % be consistent with the units of params.Fs: W can 0027 % be in Hz if and only if params.Fs is in Hz. 0028 % The default is to use form 1 with TW=3 and K=5 0029 % 0030 % pad (padding factor for the FFT) - optional (can take values -1,0,1,2...). 0031 % -1 corresponds to no padding, 0 corresponds to padding 0032 % to the next highest power of 2 etc. 0033 % e.g. For N = 500, if PAD = -1, we do not pad; if PAD = 0, we pad the FFT 0034 % to 512 points, if pad=1, we pad to 1024 points etc. 0035 % Defaults to 0. 0036 % Fs (sampling frequency) - optional. Default 1. 0037 % fpass (frequency band to be used in the calculation in the form 0038 % [fmin fmax])- optional. 0039 % Default all frequencies between 0 and Fs/2 0040 % err (error calculation [1 p] - Theoretical error bars; [2 p] - Jackknife error bars 0041 % [0 p] or 0 - no error bars) - optional. Default 0. 0042 % Output: 0043 % C (magnitude of coherency frequency x channels x channels) 0044 % phi (phase of coherency frequency x channels x channels) 0045 % S12 (cross-spectral matrix frequency x channels x channels) 0046 % f (frequencies) 0047 % confC (confidence level for C at 1-p %) - only for err(1)>=1 0048 % phistd - theoretical/jackknife (depending on err(1)=1/err(1)=2) standard deviation for phi 0049 % Note that phi + 2 phistd and phi - 2 phistd will give 95% confidence 0050 % bands for phi - only for err(1)>=1 0051 % Cerr (Jackknife error bars for C - use only for Jackknife - err(1)=2) 0052 0053 if nargin < 1; error('need data'); end; 0054 if nargin < 2; params=[]; end; 0055 [N,Ch]=size(data); 0056 if Ch==1; error('Need at least two channels of data'); end; 0057 [tapers,pad,Fs,fpass,err,trialave,params]=getparams(params); 0058 clear trialave params 0059 if nargout > 6 && err(1)~=2; 0060 error('Cerr computed only for Jackknife. Correct inputs and run again'); 0061 end; 0062 if nargout >= 4 && err(1)==0; 0063 % Errors computed only if err(1) is nonzero. Need to change params and run again. 0064 error('When errors are desired, err(1) has to be non-zero.'); 0065 end; 0066 nfft=max(2^(nextpow2(N)+pad),N); 0067 [f,findx]=getfgrid(Fs,nfft,fpass); 0068 tapers=dpsschk(tapers,N,Fs); % check tapers 0069 J=mtfftc(data,tapers,nfft,Fs); 0070 J=J(findx,:,:); 0071 if err(1)==0; 0072 [C,phi,S12]=cohmathelper(J,err); 0073 elseif err(1)==1; 0074 [C,phi,S12,confC,phistd]=cohmathelper(J,err); 0075 elseif err(1)==2; 0076 [C,phi,S12,confC,phistd,Cerr]=cohmathelper(J,err); 0077 end