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// Scilab ( http://www.scilab.org/ ) - This file is part of Scilab
// Copyright (C) INRIA - 1988 - C. Bunks
//
// This file must be used under the terms of the CeCILL.
// This source file is licensed as described in the file COPYING, which
// you should have received as part of this distribution. The terms
// are also available at
// http://www.cecill.info/licences/Licence_CeCILL_V2-en.txt
function [sm,cwp]=cspect(nlags,ntp,wtype,x,y,wpar)
//[sm,cwp]=cspect(nlags,ntp,wtype,x,y,wpar)
//Spectral estimation using the correlation method.
//Cross-spectral estimate of x and y is calculated when both
//x and y are given. Auto-spectral estimate of x is calculated
//if y is not given.
// x :data if vector, amount of input data if scalar
// y :data if vector, amount of input data if scalar
// nlags :number of correlation lags (pos. integer)
// ntp :number of transform points (pos. integer)
// wtype :window type ('re','tr','hm','hn','kr','ch')
// wpar :optional window parameters
// : for wtype='kr', wpar>0
// : for wtype='ch', 0<wpar(1)<.5, wpar(2)>0
// sm :power spectral estimate in the interval [0,1]
// cwp :calculated value of unspecified Chebyshev
// :window parameter
//
//!
[lhs,rhs]=argn(0);
if and(wtype<>['re','tr','hm','hn','kr','ch']) then
error(msprintf(gettext("%s: Wrong value for input argument #%d: Must be in the set {%s}.\n"),..
"cspect",3,"''re'',''tr'',''hm'',''hn'',''kr'',''ch''"));
end
//Analyze calling sequence and construct window
if rhs==4 then,
//cspect(nlags,ntp,wtype,x)
[w,cwp]=window(wtype,2*nlags-1);
cross=%f; //autocorrelation
elseif rhs==5 then
//cspect(nlags,ntp,wtype,x,wpar) or cspect(nlags,ntp,wtype,x,y)
if wtype=='kr' then //cspect(nlags,ntp,'kr',x,wpar)
wpar=y;
[w,cwp]=window(wtype,2*nlags-1,wpar);
cross=%f; //autocorrelation
elseif wtype=='ch' then //cspect(nlags,ntp,'ch',x,wpar)
wpar=y;
[w,cwp]=window(wtype,2*nlags-1,wpar);
cross=%f; //autocorrelation
else,//cspect(nlags,ntp,wtype,x,y)
cross=%t;//cross correlation
[w,cwp]=window(wtype,2*nlags-1);
end,
else,//cspect(nlags,ntp,wtype,x,y,wpar)
[w,cwp]=window(wtype,2*nlags-1,wpar);
cross=%t;//cross correlation
end,
//Make x and y row vectors
x=matrix(x,1,-1);
if cross then
y=matrix(y,1,-1);
if size(x,'*')<>size(y,'*') then
error(msprintf(gettext("%s: Arguments #%d and #%d must have the same sizes.\n"),"pspect",4,5));
end
end
//Estimate correlations
if size(x,'*')==1 then //Batch processing of x and y data
nsects=int(x/(3*nlags));
xlen=int(x/nsects);
ss=zeros(1,2*nlags);
if cross then,
for k=1:nsects
xk=getx(xlen,1+(k-1)*xlen);
yk=gety(xlen,1+(k-1)*xlen);
ss=corr('update',xk,yk,ss);
end
re=fft(ss,1)/x;
re=[re(nlags:-1:1) re(2:nlags)];
else
for k=1:nsects
xk=getx(xlen,1+(k-1)*xlen);
ss=corr('update',xk,ss);
end
re=fft(ss,1)/x;
re=[re(nlags:-1:1) re(2:nlags)];
end
else // Signal data given in x and y if cross-correlation
if cross then
[re1,me]=corr(x,y,nlags);
[re2,me]=corr(y,x,nlags);
re=[re1(nlags:-1:1) re2(2:nlags)];
else
[re,me]=corr(x,nlags);
re=[re(nlags:-1:1) re(2:nlags)];
end
end
//Window correlation estimate
wre=w.*re;
//Fourier transform to obtain spectral estimate
wree=[wre zeros(1,ntp-2*nlags+1)];
sm=fft(wree,-1)
//sm=abs(fft(wree,-1));
endfunction
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