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function [kr, R0]=poly2rc(a, efinal)
//poly2rc function convert prediction polynomial to reflection coefficients.
// Calling Sequence
// kr = poly2rc(a)
// [kr, R0] = rc2poly(a, efinal)
// Parameters
// a: prediction polynomial.
// efinal: final prediction error.
// kr: Return refelection coefficient.
// R0: Return the zero lag autocorrelation, R0.
// Examples
//X = [7 6 5 8 3 6]
// [kr, R0] = poly2rc(X)
//
// See also
//
// Author
// Jitendra Singh
// modified to handle empty vector as i/p by Debdeep Dey
if or(type(a)==10) then
error ('Input arguments must be double.')
end
if (size(a,1) > 1) & (size(a,2) > 1)
error ('The prediction polynomial must be stored in a vector.')
end
if argn(2)==1 | isempty(efinal) then
efinal=0;
end
if length(a)<=1 then
kr= [];
R0=efinal;
end
if a(1) ==0 then
error ('Leading coefficient cannot be zero.')
end
a=a(:)./a(1);
n=length(a)-1;
e=zeros(n,1);
if(n>=1) then
e(n)=efinal;
kr(n)=a($);
a=a';
end
if(n>=1) then
for j= (n-1):-1:1
ee=a($)
a = (a-kr(j+1)*flipdim(a,2,1))/(1-kr(j+1)^2);
a=a(1:$-1)
kr(j)=a($);
econj=conj(ee)
econj=econj'
e(j) = e(j+1)/(1.-(econj.*ee));
end
R0 = e(1)./(1-abs(kr(1))^2);
else
R0=efinal;
end
endfunction
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