Implement polystab.sci in Scilab

1 files changed, 35 insertions, 18 deletions

diff --git a/macros/polystab.sci b/macros/polystab.sci
index 84e42d4..c9da6f0 100644
--- a/macros/polystab.sci
+++ b/macros/polystab.sci
@@ -1,21 +1,38 @@
-function b = polystab(a)
-//This function stabilizes the polynomial transfer function. 
-//Calling Sequence
-//b = polystab(a)
-//Parameters 
-//a:
-//Description
-//This is an Octave function.
-//This function stabilizes the polynomial transfer function by replacing all roots outside the unit circle with their reflection inside the unit circle.
-//Examples
+function y = polystab(x)
+//Stabilize the polynomial transfer function. 
+//Calling Sequence:
+//y = polystab(x)
+//Parameters: 
+//x: real or complex valued vector
+//Description:
+//This function stabilizes the polynomial transfer function by replacing all 
+//roots outside the unit circle with their reflection inside the unit circle.
+//Example:
 //polystab([1,3,5])
-//ans  =
-//    1.    0.6    0.2  
+//ans=
+//[1, 0.6, 0.2] 
+ 
+  funcprot(0);
+  if (argn(2) ~= 1)
+    error("polystab: wrong number of input arguments");
+  end
+  root = roots(x);
+  vals = find(abs(root) > 1);
+  root(vals) = 1 ./ conj(root(vals));
+  b = x(1) * poly(root, 'x');
+  y = flipdim(coeff(b), 2);
+  if (isreal(x))
+    y = real(y);
+  end
 
-funcprot(0);
-rhs = argn(2)
-if(rhs~=1)
-error("Wrong number of input arguments.")
-end
-b = callOctave("polystab",a)
 endfunction
+
+//input validation:
+//assert_checkerror("polystab()", "polystab: wrong number of input arguments");
+//assert_checkerror("polystab(1, 2)", "Wrong number of input arguments.")
+
+//tests:
+//assert_checkalmostequal(polystab([1, 3, 5]), [1, 0.6, 0.2], %eps);
+//assert_checkequal(polystab([1; 3; 5]), polystab([1, 3, 5]));
+//assert_checkalmostequal(polystab([1+3*%i, 4+2*%i, 2+2*%i]), [1 + 3*%i, 1.35664 + 1.84888*%i, 0.88566 + 0.88566*%i], 5*10^-5);
+//assert_checkalmostequal(polystab([-1; 3+%i; -2-6*%i]), [-1, 0.3 + 0.4*%i, -0.05-0.15*%i], 5*10^-5);