mtdspectrumc

PURPOSE ^

Multi-taper frequency derivative of the spectrum - continuous process

SYNOPSIS ^

function [dS,f]=mtdspectrumc(data,phi,params)

DESCRIPTION ^

 Multi-taper frequency derivative of the spectrum - continuous process

 Usage:

 [dS,f]=mtdspectrumc(data,phi,params)
 Input: 
   Note that all times can be in arbitrary units. But the units have to be
   consistent. So, if E is in secs, win, t have to be in secs, and Fs has to
   be Hz. If E is in samples, so are win and t, and Fs=1. In case of spike
   times, the units have to be consistent with the units of data as well.
       data        (in form samples x channels/trials or a single vector) -- required
       phi         (angle for evaluation of derivative) -- required.
                       e.g. phi=[0,pi/2] gives the time and frequency derivatives
       params: structure with fields tapers, pad, Fs, fpass, 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

            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
           trialave (average over trials/channels when 1, don't average when 0) - optional. Default 0
 Output:
       dS       (spectral derivative in form phi x frequency x channels/trials if trialave=0 or 
                in form phi x frequency if trialave=1)
       f        (frequencies)

CROSS-REFERENCE INFORMATION ^

This function calls: This function is called by:

SOURCE CODE ^

0001 function [dS,f]=mtdspectrumc(data,phi,params)
0002 % Multi-taper frequency derivative of the spectrum - continuous process
0003 %
0004 % Usage:
0005 %
0006 % [dS,f]=mtdspectrumc(data,phi,params)
0007 % Input:
0008 %   Note that all times can be in arbitrary units. But the units have to be
0009 %   consistent. So, if E is in secs, win, t have to be in secs, and Fs has to
0010 %   be Hz. If E is in samples, so are win and t, and Fs=1. In case of spike
0011 %   times, the units have to be consistent with the units of data as well.
0012 %       data        (in form samples x channels/trials or a single vector) -- required
0013 %       phi         (angle for evaluation of derivative) -- required.
0014 %                       e.g. phi=[0,pi/2] gives the time and frequency derivatives
0015 %       params: structure with fields tapers, pad, Fs, fpass, 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 %
0035 %            pad            (padding factor for the FFT) - optional (can take values -1,0,1,2...).
0036 %                    -1 corresponds to no padding, 0 corresponds to padding
0037 %                    to the next highest power of 2 etc.
0038 %                       e.g. For N = 500, if PAD = -1, we do not pad; if PAD = 0, we pad the FFT
0039 %                       to 512 points, if pad=1, we pad to 1024 points etc.
0040 %                       Defaults to 0.
0041 %           Fs   (sampling frequency) - optional. Default 1.
0042 %           fpass    (frequency band to be used in the calculation in the form
0043 %                                   [fmin fmax])- optional.
0044 %                                   Default all frequencies between 0 and Fs/2
0045 %           trialave (average over trials/channels when 1, don't average when 0) - optional. Default 0
0046 % Output:
0047 %       dS       (spectral derivative in form phi x frequency x channels/trials if trialave=0 or
0048 %                in form phi x frequency if trialave=1)
0049 %       f        (frequencies)
0050 
0051 if nargin < 2; error('Need data and angle'); end;
0052 if nargin < 3; params=[]; end;
0053 [tapers,pad,Fs,fpass,err,trialave,params]=getparams(params);
0054 clear err params
0055 data=change_row_to_column(data);
0056 N=size(data,1);
0057 nfft=max(2^(nextpow2(N)+pad),N);
0058 [f,findx]=getfgrid(Fs,nfft,fpass); 
0059 tapers=dpsschk(tapers,N,Fs); % check tapers
0060 K=size(tapers,2);
0061 J=mtfftc(data,tapers,nfft,Fs);
0062 J=J(findx,:,:);
0063 A=sqrt(1:K-1);
0064 A=repmat(A,[size(J,1) 1]);
0065 A=repmat(A,[1 1 size(J,3)]);
0066 S=squeeze(mean(J(:,1:K-1,:).*A.*conj(J(:,2:K,:)),2));
0067 if trialave; S=squeeze(mean(S,2));end;
0068 nphi=length(phi);
0069 for p=1:nphi;
0070     dS(p,:,:)=real(exp(i*phi(p))*S);
0071 end;
0072 dS=squeeze(dS);
0073 dS=change_row_to_column(dS);

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