fftindex.m

Matlab时频分析工具箱,希望能对大家有所帮助啊

function n=fftindex(N,nyquestzero)
%FFTINDEX  Frequency index of FFT modulations
%   Usage: n=fftindex(N);
%
%   FFTINDEX(N) returns the index of the frequencies of the standard FFT of
%   length N as the are ordered in the output from the FFT routine.
%
%   FFTINDEX(N,0) does as above, but sets the Nyquest frequency to zero.
%
%   SEE ALSO: DFT

% This program is free software: you can redistribute it and/or modify
% it under the terms of the GNU General Public License as published by
% the Free Software Foundation, either version 3 of the License, or
% (at your option) any later version.
% 
% This program is distributed in the hope that it will be useful,
% but WITHOUT ANY WARRANTY; without even the implied warranty of
% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
% GNU General Public License for more details.
% 
% You should have received a copy of the GNU General Public License
% along with this program.  If not, see <http://www.gnu.org/licenses/>.
  
error(nargchk(1,2,nargin));

if nargin ==1
  if rem(N,2)==0
    n=[0:N/2,-N/2+1:-1].';
  else
    n=[0:(N-1)/2,-(N-1)/2:-1].';
  end;
else
  if rem(N,2)==0
    n=[0:N/2-1,0,-N/2+1:-1].';
  else
    n=[0:(N-1)/2,-(N-1)/2:-1].';
  end;  
end;