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# mtfftc

## PURPOSE Multi-taper fourier transform - continuous data

## SYNOPSIS function J=mtfftc(data,tapers,nfft,Fs)

## DESCRIPTION ``` Multi-taper fourier transform - continuous data

Usage:
J=mtfftc(data,tapers,nfft,Fs) - all arguments required
Input:
data (in form samples x channels/trials or a single vector)
tapers (precalculated tapers from dpss)
Fs   (sampling frequency)

Output:
J (fft in form frequency index x taper index x channels/trials)```

## CROSS-REFERENCE INFORMATION This function calls:
This function is called by:
• CrossSpecMatc Multi-taper cross-spectral matrix - another routine, allows for multiple trials and channels
• coherencyc Multi-taper coherency,cross-spectrum and individual spectra - continuous process
• coherencyc_unequal_length_trials This routine computes the average multi-taper coherence for a given set of unequal length segments. It is
• cohmatrixc Multi-taper coherency,cross-spectral matrix - continuous process
• ftestc computes the F-statistic for sine wave in locally-white noise (continuous data).
• mtdspectrumc Multi-taper frequency derivative of the spectrum - continuous process
• mtspectrumc Multi-taper spectrum - continuous process
• mtspectrumc_unequal_length_trials This routine computes the multi-taper spectrum for a given set of unequal length segments. It is
• mtspectrumsegc Multi-taper segmented spectrum for a univariate continuous process
• nonst_stat Nonstationarity test - continuous process

## SOURCE CODE ```0001 function J=mtfftc(data,tapers,nfft,Fs)
0002 % Multi-taper fourier transform - continuous data
0003 %
0004 % Usage:
0005 % J=mtfftc(data,tapers,nfft,Fs) - all arguments required
0006 % Input:
0007 %       data (in form samples x channels/trials or a single vector)
0008 %       tapers (precalculated tapers from dpss)
0009 %       nfft (length of padded data)
0010 %       Fs   (sampling frequency)
0011 %
0012 % Output:
0013 %       J (fft in form frequency index x taper index x channels/trials)
0014 if nargin < 4; error('Need all input arguments'); end;
0015 data=change_row_to_column(data);
0016 [NC,C]=size(data); % size of data
0017 [NK K]=size(tapers); % size of tapers
0018 if NK~=NC; error('length of tapers is incompatible with length of data'); end;
0019 tapers=tapers(:,:,ones(1,C)); % add channel indices to tapers
0020 data=data(:,:,ones(1,K)); % add taper indices to data
0021 data=permute(data,[1 3 2]); % reshape data to get dimensions to match those of tapers
0022 data_proj=data.*tapers; % product of data with tapers
0023 J=fft(data_proj,nfft)/Fs;   % fft of projected data```

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