largestr.m

Matlab时频分析工具箱,希望能对大家有所帮助啊

function [xo,N]=largestr(xi,p,mtype)
%LARGESTR   Keep largest ratio of coefficients.
%   Usage:  xo=LARGESTR(x,p);
%           [xo,N]=LARGESTR(x,p);
%           xo=LARGESTR(x,p,mtype);
%           [xo,N]=LARGESTR(x,p,mtype);
%
%   LARGESTR(x,p) returns an array of the same size as x keeping
%   the fraction p of the coefficients. The coefficients with the largest
%   magnitude are kept.
%
%   [xo,N]=LARGESTR(xi,p) will additionally return the number of
%   coefficients kept.
%
%   LARGESTR(x,p,'full') returns the output as a full matrix. This is the
%   default.
%
%   LARGESTR(x,p,'sparse') returns the output as a sparse matrix.
% 
%   Note that if this function is used on coefficients coming from a
%   redundant transform or from a transform where the input signal was
%   padded, the coefficient array will be larger than the original input
%   signal. Therefore, the number of coefficients kept might be higher
%   than expected.
%
%   SEE ALSO:  LARGESTN
%
%   REFERENCES:
%     S. Mallat. A wavelet tour of signal processing. Academic Press, San
%     Diego, CA, 1998.
%     

% 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(2,3,nargin));

if (prod(size(p))~=1 || ~isnumeric(p))
  error('p must be a scalar.');
end;

if nargin==2
  mtype='full';
end;

% Determine the size of the array.
ss=prod(size(xi));

N=round(ss*p);

xo=largestn(xi,N,mtype);