Multi-taper time-frequency spectrum - continuous process
Usage:
[S,t,f,Serr]=mtspecgramc(data,movingwin,params)
Input:
Note units have to be consistent. Thus, if movingwin is in seconds, Fs
has to be in Hz. see chronux.m for more information.
data (in form samples x channels/trials) -- required
movingwin (in the form [window winstep] i.e length of moving
window and step size)
Note that units here have
to be consistent with
units of Fs - required
params: structure with fields tapers, pad, Fs, fpass, err, 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
Note that T has to be equal to movingwin(1).
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
err (error calculation [1 p] - Theoretical error bars; [2 p] - Jackknife error bars
[0 p] or 0 - no error bars) - optional. Default 0.
trialave (average over trials/channels when 1, don't average when 0) - optional. Default 0
Output:
S (spectrum in form time x frequency x channels/trials if trialave=0; in the form time x frequency if trialave=1)
t (times)
f (frequencies)
Serr (error bars) only for err(1)>=10001 function [S,t,f,Serr]=mtspecgramc(data,movingwin,params) 0002 % Multi-taper time-frequency spectrum - continuous process 0003 % 0004 % Usage: 0005 % [S,t,f,Serr]=mtspecgramc(data,movingwin,params) 0006 % Input: 0007 % Note units have to be consistent. Thus, if movingwin is in seconds, Fs 0008 % has to be in Hz. see chronux.m for more information. 0009 % data (in form samples x channels/trials) -- required 0010 % movingwin (in the form [window winstep] i.e length of moving 0011 % window and step size) 0012 % Note that units here have 0013 % to be consistent with 0014 % units of Fs - required 0015 % params: structure with fields tapers, pad, Fs, fpass, err, trialave 0016 % - optional 0017 % tapers : precalculated tapers from dpss or in the one of the following 0018 % forms: 0019 % (1) A numeric vector [TW K] where TW is the 0020 % time-bandwidth product and K is the number of 0021 % tapers to be used (less than or equal to 0022 % 2TW-1). 0023 % (2) A numeric vector [W T p] where W is the 0024 % bandwidth, T is the duration of the data and p 0025 % is an integer such that 2TW-p tapers are used. In 0026 % this form there is no default i.e. to specify 0027 % the bandwidth, you have to specify T and p as 0028 % well. Note that the units of W and T have to be 0029 % consistent: if W is in Hz, T must be in seconds 0030 % and vice versa. Note that these units must also 0031 % be consistent with the units of params.Fs: W can 0032 % be in Hz if and only if params.Fs is in Hz. 0033 % The default is to use form 1 with TW=3 and K=5 0034 % Note that T has to be equal to movingwin(1). 0035 % 0036 % pad (padding factor for the FFT) - optional. Defaults to 0. 0037 % e.g. For N = 500, if PAD = 0, we pad the FFT 0038 % to 512 points; if PAD = 2, we pad the FFT 0039 % to 2048 points, etc. 0040 % Fs (sampling frequency) - optional. Default 1. 0041 % fpass (frequency band to be used in the calculation in the form 0042 % [fmin fmax])- optional. 0043 % Default all frequencies between 0 and Fs/2 0044 % err (error calculation [1 p] - Theoretical error bars; [2 p] - Jackknife error bars 0045 % [0 p] or 0 - no error bars) - optional. Default 0. 0046 % trialave (average over trials/channels when 1, don't average when 0) - optional. Default 0 0047 % Output: 0048 % S (spectrum in form time x frequency x channels/trials if trialave=0; in the form time x frequency if trialave=1) 0049 % t (times) 0050 % f (frequencies) 0051 % Serr (error bars) only for err(1)>=1 0052 0053 if nargin < 2; error('Need data and window parameters'); end; 0054 if nargin < 3; params=[]; end; 0055 0056 if length(params.tapers)==3 & movingwin(1)~=params.tapers(2); 0057 error('Duration of data in params.tapers is inconsistent with movingwin(1), modify params.tapers(2) to proceed') 0058 end 0059 0060 [tapers,pad,Fs,fpass,err,trialave,params]=getparams(params); 0061 if nargout > 3 && err(1)==0; 0062 % Cannot compute error bars with err(1)=0. change params and run again. 0063 error('When Serr is desired, err(1) has to be non-zero.'); 0064 end; 0065 0066 N=size(data,1); 0067 Nwin=round(Fs*movingwin(1)); % number of samples in window 0068 Nstep=round(movingwin(2)*Fs); % number of samples to step through 0069 nfft=2^(nextpow2(Nwin)+pad); 0070 0071 [f,findx]=getfgrid(Fs,nfft,fpass); 0072 tapers=dpsschk(tapers,Nwin,Fs); % check tapers 0073 [NC C]=size(data); % size of data 0074 [NK K]=size(tapers); % size of tapers 0075 0076 tapers=tapers(:,:,ones(1,C)); % add channel indices to tapers 0077 0078 if NK~=Nwin ; error('length of tapers is incompatible with length of data'); end; 0079 0080 winstart=1:Nstep:N-Nwin+1; 0081 nw=length(winstart); 0082 0083 S = zeros(nw,length(f),C); 0084 0085 for n=1:nw; 0086 J=fft((permute(data(winstart(n):winstart(n)+Nwin-1,:,ones(1,K)),[1 3 2]) .* tapers) ,nfft)/Fs; % fft of projected data 0087 J=J(findx,:,:); 0088 S(n,:,:)=squeeze(mean(conj(J).*J,2)); 0089 end 0090 0091 if nargout==4;Serr=squeeze(Serr);end; 0092 winmid=winstart+round(Nwin/2); 0093 t=winmid/Fs;