function [tfd, t, f] = spec2(x, fs, nfreq, decf, w, how)% spec2 -- Compute samples of the type II spectrogram.%%  Usage%    [tfd, t, f] = spec2(x, fs, nfreq, decf, w, how)%%  Inputs%    x      signal vector%    fs     sampling frequency of x (optional, default is 1 sample/second)%    nfreq  number of samples to compute in frequency (optional, default%           is 256)%    decf   sub-sampling factor in time of the stft (optional, default %           is 1, i.e. no sub-sampling)%    w      if length(w)==1 then the window is a guassian with duration 'w'%           (see chirplets.m), otherwise 'w' is the window.  'w' must have an%           odd length to have a center point. (optional, default is a %           gaussian with a duration of 5)%    how    if how='short' then the stft is computed for the same times%           as the signal and %               size(tfd,2) = length(x)%           if how='long' then the stft will be computed for times before%           and after the times of the signal and%               size(tfd,2) = length(x) + length(w) - 1%           (optional, default is 'short')%%  Outputs%    tfd  matrix containing the spectrogram of signal x (optional)%    t    vector of sampling times (optional)%    f    vector of frequency values (optional)%% If no output arguments are specified, then the spectrogram is% displayed using ptfd(tfd, t, f).% Copyright (C) -- see DiscreteTFDs/Copyrighterror(nargchk(1, 6, nargin));if (nargin == 1)  [tfd, t, f] = stft2(x);elseif (nargin == 2)  [tfd, t, f] = stft2(x, fs);elseif (nargin == 3)  [tfd, t, f] = stft2(x, fs, nfreq);elseif (nargin == 4)  [tfd, t, f] = stft2(x, fs, nfreq, decf);elseif (nargin == 5)  [tfd, t, f] = stft2(x, fs, nfreq, decf, w);elseif (nargin == 6)  [tfd, t, f] = stft2(x, fs, nfreq, decf, w, how);endtfd = real(tfd.*conj(tfd));if (nargout == 0)  ptfd(tfd, t, f);  clear tfdend