1 files changed, 30 insertions, 31 deletions
diff --git a/macros/cheb.sci b/macros/cheb.sci
index db2df85..1ebf3a0 100644
--- a/macros/cheb.sci
+++ b/macros/cheb.sci
@@ -1,34 +1,33 @@
-function res = cheb (n, x)
-//Calculates the nth-order Chebyshev polynomial at the point x.
-//Calling Sequence
-//cheb(n, x)
-//Parameters 
-//n: Filter order
-//x: Point at which the Chebyshev polynomial is calculater. 
-//Description
-//This is an Octave function.
-//Equation for Chebyshev polynomial is
-//           / cos(n acos(x),    |x| <= 1
-//   Tn(x) = |
-//           \ cosh(n acosh(x),  |x| > 1
-//
-//x can also be a vector. In that case the output will also be a vector of same size as x.
-//Examples
-//x = [1 2 3 4]
-// cheb(10, x)
-//ans =
-//
-//   1.0000e+00   2.6209e+05   2.2620e+07   4.5747e+08
+function T = cheb (n, x)
 
-funcprot(0);
-rhs = argn(2)
-if (rhs < 2 | rhs > 2)
-error("Wrong number of input arguments.")
-end
+ funcprot(0);
+    rhs= argn(2);
+
+  if (rhs ~= 2)
+    error("Wrong Number of input arguments");
+  elseif (~(isscalar (n) & (n == round(n)) & (n >= 0)))
+    error ("cheb: n has to be a positive integer");
+  end
+
+  if (max(size(x)) == 0)
+    T = [];
+  end
+  // avoid resizing latencies
+  T = zeros(size(x));
+  ind = (abs (x) <= 1);
+  if (max(size(ind)))
+    T(ind) = cos(n*acos(x(ind)));
+  end
+
+  ind = abs (x) > 1;
+  if (max(size(ind)))
+    T(ind) = cosh(n*acosh(x(ind)));
+  end
+
+  T = real(T);
+
+  if(size(x)==[1 1])
+    T=T(1);
+  end
 
-select(rhs)
-	
-	case 2 then
-		res = callOctave("cheb",n,x)
-	end
 endfunction