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function [B,A,C] = invfreqz(H,F,nB,nA,W,iter,tol,trace)
//Fit filter B(z)/A(z)to the complex frequency response H at frequency points F. A and B are real polynomial coefficients of order nA and nB.
//Calling Sequence
//[B,A,C] = invfreqz(H,F,nB,nA,W,iter,tol,trace)
//[B,A,C] = invfreqz(H,F,nB,nA,W)
//[B,A,C] = invfreqz(H,F,nB,nA)
//Parameters
//H: desired complex frequency response.
//F: frequency (must be same length as H).
//nB: order of the numerator polynomial B.
//nA: order of the denominator polynomial A.
//W: vector of weights (must be same length as F).
//Description
//This is an Octave function.
//Fit filter B(z)/A(z)to the complex frequency response H at frequency points F. A and B are real polynomial coefficients of order nA and nB.
//Optionally, the fit-errors can be weighted vs frequency according to the weights W.
//Note: all the guts are in invfreq.m
//Examples
//[B,A] = butter(4,1/4);
//[H,F] = freqz(B,A);
//[Bh,Ah,C] = invfreq(H,F,4,4)
//Bh =
//
// 0.010209 0.040838 0.061257 0.040838 0.010209
//
//Ah =
//
// 1.00000 -1.96843 1.73586 -0.72447 0.12039
//
//C = -7.7065e-15
funcprot(0);
lhs = argn(1)
rhs = argn(2)
if (rhs < 4 | rhs > 8)
error("Wrong number of input arguments.")
end
select(rhs)
case 4 then
if(lhs==1)
B = callOctave("invfreqz",H,F,nB,nA)
elseif(lhs==2)
[B, A] = callOctave("invfreqz",H,F,nB,nA)
elseif(lhs==3)
[B, A, C] = callOctave("invfreqz",H,F,nB,nA)
else
error("Wrong number of output argments.")
end
case 5 then
if(lhs==1)
B = callOctave("invfreqz",H,F,nB,nA,W)
elseif(lhs==2)
[B, A] = callOctave("invfreqz",H,F,nB,nA,W)
elseif(lhs==3)
[B, A, C] = callOctave("invfreqz",H,F,nB,nA,W)
else
error("Wrong number of output argments.")
end
case 6 then
if(lhs==1)
B = callOctave("invfreqz",H,F,nB,nA,W,iter)
elseif(lhs==2)
[B, A] = callOctave("invfreqz",H,F,nB,nA,W,iter)
elseif(lhs==3)
[B, A, C] = callOctave("invfreqz",H,F,nB,nA,W,iter)
else
error("Wrong number of output argments.")
end
case 7 then
if(lhs==1)
B = callOctave("invfreqz",H,F,nB,nA,W,iter,tol)
elseif(lhs==2)
[B, A] = callOctave("invfreqz",H,F,nB,nA,W,iter,tol)
elseif(lhs==3)
[B, A, C] = callOctave("invfreqz",H,F,nB,nA,W,iter,tol)
else
error("Wrong number of output argments.")
end
case 8 then
if(lhs==1)
B = callOctave("invfreqz",H,F,nB,nA,W,iter,tol,trace)
elseif(lhs==2)
[B, A] = callOctave("invfreqz",H,F,nB,nA,W,iter,tol,trace)
elseif(lhs==3)
[B, A, C] = callOctave("invfreqz",H,F,nB,nA,W,iter,tol,trace)
else
error("Wrong number of output argments.")
end
end
endfunction
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