From 9490efa64326dfe296ab2da9fed041630b1d992c Mon Sep 17 00:00:00 2001
From: Chandra Pratap
Date: Wed, 7 Aug 2024 17:55:41 +0530
Subject: Implement tf2sos.sci in Scilab

---
 macros/tf2sos.sci | 83 +++++++++++++++++++++++++++++++++++++++----------------
 1 file changed, 59 insertions(+), 24 deletions(-)

diff --git a/macros/tf2sos.sci b/macros/tf2sos.sci
index 7570707..ad7f10d 100644
--- a/macros/tf2sos.sci
+++ b/macros/tf2sos.sci
@@ -1,35 +1,70 @@
-function [sos,varargout] = tf2sos (b, a)
+function [sos,g] = tf2sos (B, A)
 //This function converts direct-form filter coefficients to series second-order sections.
-//Calling Sequence
+//Calling Sequence:
 //[sos] = tf2sos (b, a)
 //[sos, g] = tf2sos (b, a)
-//Parameters 
+//Parameters:
 //b: matrix of real numbers
 //a: matrix of real numbers 
-//Description
-//This is an Octave function.
+//Description:
 //This function converts direct-form filter coefficients to series second-order sections.
 //The input parameters b and a are vectors specifying the digital filter H(z) = B(z)/A(z). 
 //The output is the sos matrix and the overall gain.
 //If there is only one output argument, the overall filter gain is applied to the first second-order section in the sos matrix.
-//Examples
+//Examples:
 //tf2sos([1,2,3,4,5,6],2)
 //ans =
-//   0.50000   0.80579   1.07239   1.00000   0.00000   0.00000
-//   1.00000  -1.10337   1.87524   1.00000   0.00000   0.00000
-//   1.00000   1.49180  -0.00000   1.00000   0.00000   0.00000
-
-funcprot(0);
-rhs = argn(2)
-lhs = argn(1)
-
-if(rhs~=2)
-error("Wrong number of input arguments.")
-end
-	select(lhs)
-	case 1 then
-	sos = callOctave("tf2sos",b,a)
-	case 2 then
-	[sos,g] = callOctave("tf2sos",b,a)
-	end
-endfunction 
+//   0.50000   0.80579   1.07239   0.00000   0.00000   1.00000
+//   1.00000  -1.10337   1.87524   0.00000   0.00000   1.00000
+//   1.00000   1.49180  -0.00000   0.00000   1.00000   0.00000
+
+  funcprot(0);
+  if (nargin() ~= 2) then
+    error("Wrong number of input arguments.");
+  end
+  S = syslin([], inv_coeff(flipdim(B(:)', 2)), inv_coeff(flipdim(A(:)', 2)));
+  [z,p,k] = tf2zp(S);
+  if (nargout() < 2)
+    sos = clean(zp2sos(z,p,k));
+  else
+    [sos,g] = clean(zp2sos(z,p,k));
+  end
+
+endfunction
+
+//tests:
+//assert_checkerror("tf2sos(1)", "Wrong number of input arguments.");
+//assert_checkerror("tf2sos(1, 2, 3)", "Wrong number of input arguments.");
+
+//A = [-7 -12];
+//B = [-1 -7];
+//assert_checkequal(tf2sos(A, B), [7 12 0 1 7 0]);
+
+//A = [1 2; 3 4];
+//B = [3 2; 1 4];
+//assert_checkalmostequal(tf2sos(A, B), [0.3333 0.0679 0.4768 1 -0.6667 1.3333; 1 2.7963 0 1 1 0], 5*10^-4);
+
+//A = [1 1 1 1];
+//B = [-1 -1; -1 -1];
+//assert_checkalmostequal(tf2sos(A, B), [-1 0 -1 1 0 1; 1 1 0 1 1 0], 100*%eps);
+
+//b = [1, 1];  
+//a = [1, 2];  
+//expected_sos = [1, 1, 0, 1, 2, 0];
+//sos = tf2sos(b, a);
+//assert_checkalmostequal(sos, expected_sos, %eps);
+
+//b = [1, 2, 2];
+//a = [1, -1, 1];  
+//expected_sos = [1, 2, 2, 1, -1, 1];
+//sos = tf2sos(b, a);
+//assert_checkalmostequal(sos, expected_sos, 100*%eps);
+
+//b = [1, 1, 1, 1];  
+//a = [1, 1, 1, 1];  
+//expected_sos = [
+//    1, 0, 1, 1, 0, 1;
+//    1, 1, 0, 1, 1, 0
+//];
+//sos = tf2sos(b, a);
+//assert_checkalmostequal(sos, expected_sos, 100*%eps);
-- 
cgit