makeprocess.sci

小波分解源代码

function x = MakeProcess(NR,N);
// x = MakeProcess(NR,N);
// Description :
//   Generates NR locally stationary process realizations
//    by filtering a white noise (z) through a slowly varying filter (kernel);
//   The filtering is done by convolution in the time-domain. 
//
// Inputs
//	NR  : number of realizations
//       N   : size of signal
//
// Outputs
//  	x   : N*NR matrix containing NR realizations of a 
//             locally stationary process
//
//  Copyright Aldo I Maalouf

  x = zeros(N,NR);
  gammaa = (N/2) * %pi;       // center frequency
  par = 1000;               // the greater par, the slower the variation 
  M = N/16;
  enveloppe = ones(1,N); // the rising cutoff function 
  start = (1:M);       // the rising cutoff interval
  enveloppe(start) = (1+sin(-%pi/2+(start-ones(1,M))./(M-1)*%pi))/2;
  enveloppe(N-M+1:N) = reverse(enveloppe(1:M));
// ---------- the lsp (x) -----------------------------------
  beta = .3;
  for i = 1:NR,
   z= WhiteNoise(ones(1,N));
   for j = 1:N,
    d = (j-1)./N - (1:N)./N;
   end;
  end;
  beta = .01;
  for i = 1:N,
    j = (1:N)-i;
    sa = 1+(i>M) * beta * (i-M);
    filter = exp(-(j./sa).^2/2)./%pi./sa;
    filter = enveloppe(i).* (filter ./sum(filter));
   filter = filter .* cos(%pi.*j./4);
    x(i) = sum(z.*filter);
  end
  endfunction