Home > chronux > test > mtspecgramc_fast.m

# mtspecgramc_fast

## PURPOSE

Multi-taper time-frequency spectrum - continuous process

## SYNOPSIS

function [S,t,f,Serr]=mtspecgramc(data,movingwin,params)

## DESCRIPTION

``` 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
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).

e.g. For N = 500, if PAD = 0, 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)>=1```

## CROSS-REFERENCE INFORMATION

This function calls:
This function is called by:

## SOURCE CODE

```0001 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
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
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;```

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