1 files changed, 79 insertions, 46 deletions
diff --git a/macros/besselap.sci b/macros/besselap.sci
index 6fe4f47..2ed0047 100644
--- a/macros/besselap.sci
+++ b/macros/besselap.sci
@@ -1,48 +1,81 @@
-function [zero, pole, gain] = besselap (n)
-//Return bessel analog filter prototype.
-//Calling Sequence
-//[zero, pole, gain] = besselap (n)
-//[zero, pole] = besselap (n)
-//zero = besselap (n)
-//Parameters 
-//n: Filter Order
-//zero: Zeros
-//pole: Poles
-//gain: Gain
-//Description
-//This is an Octave function.
-//It Return bessel analog filter prototype of nth order.
-//Examples
-//[zero, pole, gain] = besselap (5)
-//zero = [](0x0)
-//pole =
+// Copyright (C) 2018 - IIT Bombay - FOSSEE
 //
-//  -0.59058 + 0.90721i
-//  -0.59058 - 0.90721i
-//  -0.92644 + 0.00000i
-//  -0.85155 + 0.44272i
-//  -0.85155 - 0.44272i
-//
-//gain =  1
-
-funcprot(0);
-lhs = argn(1)
-rhs = argn(2)
-if (rhs < 1 | rhs > 1)
-error("Wrong number of input arguments.")
-end
-
-select(rhs)
-	
-	case 1 then
-		if(lhs==1)
-		zero = callOctave("besselap",n)
-		elseif(lhs==2)
-		[zero, pole] = callOctave("besselap",n)
-		elseif(lhs==3)
-		[zero, pole, gain] = callOctave("besselap",n)
-		else
-		error("Wrong number of output argments.")
-		end
-	end
+// 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 contribution: FOSSEE, IIT Bombay
+// Original Source : https://octave.sourceforge.io/signal/
+// Modifieded by: Sonu Sharma, RGIT Mumbai
+// Organization: FOSSEE, IIT Bombay
+// Email: toolbox@scilab.in
+
+
+function [zero, pole, gain]=besselap(n)
+    //Bessel analog filter prototype.
+
+    //Calling Sequence
+    //[zero, pole, gain] = besselap(n)
+    //zero = besselap(n)
+
+    //Parameters
+    //n: Filter Order
+    //zero: Zeros
+    //pole: Poles
+    //gain: Gain
+
+    //Description
+    //It Return bessel analog filter prototype of nth order.
+
+    //Examples
+    //[zero, pole, gain] = besselap (5)
+    //Output :
+    // gain  =
+    //
+    //    1.
+    // pole  =
+    //
+    //  - 0.5905759 + 0.9072068i
+    //  - 0.5905759 - 0.9072068i
+    //  - 0.9264421
+    //  - 0.8515536 + 0.4427175i
+    //  - 0.8515536 - 0.4427175i
+    // zero  =
+    //
+    //     []
+
+
+
+    funcprot(0);
+    [nargout, nargin] = argn() ;
+
+    if (nargin>1 | nargin<1)
+        error("besselap : wrong number of input argument")
+    end
+
+    // interpret the input parameters
+    if (~(length(n)==1 & n == round(n) & n > 0))
+        error ("besselap: filter order n must be a positive integer");
+    end
+
+    p0=1;
+    p1=[1 1];
+    for nn=2:n
+        px=(2*nn-1)*p1;
+        py=[p0 0 0];
+        px=prepad(px,max(length(px),length(py)),0);
+        py=prepad(py,length(px));
+        p0=p1;
+        p1=px+py;
+    end
+    // p1 now contains the reverse bessel polynomial for n
+
+    // scale it by replacing s->s/w0 so that the gain becomes 1
+    p1=p1.*p1(length(p1)).^((length(p1)-1:-1:0)/(length(p1)-1));
+
+    zero=[];
+    pole=roots(p1);
+    gain=1;
+
 endfunction