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// Copyright (C) 2018 - IIT Bombay - FOSSEE
// 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
// Original Source : https://octave.sourceforge.io/signal/
// Modifieded by: Abinash Singh Under FOSSEE Internship
// Date of Modification: 3 Feb 2024
// Organization: FOSSEE, IIT Bombay
// Email: toolbox@scilab.in
function [z,p,k]=tf2zp(num,den)
// Transfer function to zero pole conversion
//Calling Sequence
//[z,p,k]= tf2zp(b,a);
//Parameters
//z=zeros of the corrsponding tf
//p=poles of the corresponding tf
//k=gain of the tf
//b=vector containing the numerator coefficients of the transfer function in descending powers of s/z
//a=vector containing the denominator coefficients of the transfer function in descending powers of s/z
//For discrete-time transfer functions, it is highly recommended to
//make the length of the numerator and denominator equal to ensure
//correct results. You can do this using the function EQTFLENGTH in
//the Signal Processing Toolbox.
//Author : Debdeep Dey
//Example :
//b = [1 2 3];
//a = [4 5 6];
//[z p k] = tf2zp(b,a)
//Output:
//k =
//
// 0.25
// p =
//
// - 0.625 + 1.0532687i
// - 0.625 - 1.0532687i
// z =
//
// - 1. + 1.4142136i
// - 1. - 1.4142136i
numop=argn(1);
//take only the first row of numerator into consideration
num=num(1,:);
//remove leading columns of zeros from numerator
if ~isempty(num) then
while(num(:,1)==0 & length(num)>1)
num(:,1)=[];
end
end
[rd,cod]=size(den);
[ny,np]=size(num);
if(rd>1) then
error("Denominator must be row vector");
// elseif np>cod then
// error("Improper transfer function"); it is a bug it should be removed
end
if (~isempty(den)) then
coef=den(1);
else
coef=1;
end
if coef ==0 then
error("Denominator must have non zero leading coefficient");
end
//remove leading columns of zeros from numerator
if ~isempty(num) then
while(num(:,1)==0 & length(num)>1)
num(:,1)=[];
end
end
if (find(den==%inf) ~= [] | find(num==%inf) ~= []) then
error("Input to ROOTS must not contain NaN or Inf")
end
//poles
p=roots(den);
//zeros and gain
k=zeros(ny,1);
linf=%inf;
z=linf(ones(np-1,1),ones(ny,1));
for i=1:ny
zz=roots(num(i,:));
if ~isempty(zz), z(1:length(zz), i) = zz; end
ndx = find(num(i,:)~=0);
if ~isempty(ndx), k(i,1) = num(i,ndx(1))./coef; end
end
z=roots(num);
endfunction
/*
Note : This function is tested with Octave's outputs as a reference.
[z p k] = tf2zp([9.6500e+02 -1.1773e+05 3.8648e+06 -4.5127e+071.5581e+08],[ 1 -3 2]) //pass
[z p k] = tf2zp([1 2 3 4],[ 1 -3 2]) //pass
[z p k] = tf2zp([4 5 6],[1]) // pass
*/
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