getfgrid

PURPOSE

SYNOPSIS

DESCRIPTION

 Helper function that gets the frequency grid associated with a given fft based computation
 Called by spectral estimation routines to generate the frequency axes 
 Usage: [f,findx]=getfgrid(Fs,nfft,fpass)
 Inputs:
 Fs        (sampling frequency associated with the data)-required
 nfft      (number of points in fft)-required
 fpass     (band of frequencies at which the fft is being calculated [fmin fmax] in Hz)-required
 Outputs:
 f         (frequencies)
 findx     (index of the frequencies in the full frequency grid). e.g.: If
 Fs=1000, and nfft=1048, an fft calculation generates 512 frequencies
 between 0 and 500 (i.e. Fs/2) Hz. Now if fpass=[0 100], findx will
 contain the indices in the frequency grid corresponding to frequencies <
 100 Hz. In the case fpass=[0 500], findx=[1 512].

CROSS-REFERENCE INFORMATION

• CrossSpecMat
• 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
• cohgramc Multi-taper time-frequency coherence,cross-spectrum and individual spectra - continuous processes
• cohmatrixc Multi-taper coherency,cross-spectral matrix - continuous process
• ftestc computes the F-statistic for sine wave in locally-white noise (continuous data).
• mtdspecgramc Multi-taper derivative of the time-frequency spectrum - continuous process
• mtdspectrumc Multi-taper frequency derivative of the spectrum - continuous process
• mtspecgramc Multi-taper time-frequency spectrum - continuous process
• mtspectrum_of_spectrumc Multi-taper segmented, second spectrum (spectrum of the log spectrum) for a 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
• spsvd Space frequency SVD of input data - continuous processes
• coherencycpb Multi-taper coherency,cross-spectrum and individual spectra - continuous and binned point process data
• coherencycpt Multi-taper coherency,cross-spectrum and individual spectra -continuous data and point process as times
• cohgramcpb Multi-taper time-frequency coherence,cross-spectrum and individual spectra
• cohgramcpt Multi-taper time-frequency coherence,cross-spectrum and individual spectra
• CrossSpecMatpb
• coherencypb Multi-taper coherency,cross-spectrum and individual spectra - binned point process
• cohgrampb Multi-taper time-frequency coherence,cross-spectrum and individual spectra - two binned point processes
• cohmatrixpb Multi-taper coherency matrix - binned point process
• mtdspecgrampb Multi-taper derivatives of time-frequency spectrum - binned point process
• mtdspectrumpb Multi-taper spectral derivative - binned point process
• mtspecgrampb Multi-taper time-frequency spectrum - binned point process
• mtspectrumpb Multi-taper spectrum - binned point process
• mtspectrumsegpb Multi-taper segmented spectrum for a univariate binned point process
• CrossSpecMatpt
• coherencypt Multi-taper coherency - point process times
• cohgrampt Multi-taper time-frequency coherence - two point processes given as times
• cohmatrixpt Multi-taper coherency matrix - point process times
• mtdspecgrampt Multi-taper derivative time-frequency spectrum - point process times
• mtdspectrumpt Multi-taper spectral derivative - point process times
• mtspecgrampt Multi-taper time-frequency spectrum - point process times
• mtspectrumpt Multi-taper spectrum - point process times
• mtspectrumsegpt Multi-taper segmented spectrum for a univariate binned point process
• mtspecgramc_fast Multi-taper time-frequency spectrum - continuous process
• mtspecgramc_slow Multi-taper time-frequency spectrum - continuous process

SOURCE CODE

0001 function [f,findx]=getfgrid(Fs,nfft,fpass)
0002 % Helper function that gets the frequency grid associated with a given fft based computation
0003 % Called by spectral estimation routines to generate the frequency axes
0004 % Usage: [f,findx]=getfgrid(Fs,nfft,fpass)
0005 % Inputs:
0006 % Fs        (sampling frequency associated with the data)-required
0007 % nfft      (number of points in fft)-required
0008 % fpass     (band of frequencies at which the fft is being calculated [fmin fmax] in Hz)-required
0009 % Outputs:
0010 % f         (frequencies)
0011 % findx     (index of the frequencies in the full frequency grid). e.g.: If
0012 % Fs=1000, and nfft=1048, an fft calculation generates 512 frequencies
0013 % between 0 and 500 (i.e. Fs/2) Hz. Now if fpass=[0 100], findx will
0014 % contain the indices in the frequency grid corresponding to frequencies <
0015 % 100 Hz. In the case fpass=[0 500], findx=[1 512].
0016 if nargin < 3; error('Need all arguments'); end;
0017 df=Fs/nfft;
0018 f=0:df:Fs; % all possible frequencies
0019 f=f(1:nfft);
0020 if length(fpass)~=1;
0021    findx=find(f>=fpass(1) & f<=fpass(end));
0022 else
0023    [fmin,findx]=min(abs(f-fpass));
0024    clear fmin
0025 end;
0026 f=f(findx);