code changes by Sonu Sharma during FOSSEE Fellowship 2018

1 files changed, 85 insertions, 54 deletions

diff --git a/macros/chirp.sci b/macros/chirp.sci
index 41a94e6..c8acdeb 100644
--- a/macros/chirp.sci
+++ b/macros/chirp.sci
@@ -1,55 +1,86 @@
-function [y] = chirp(t,f0,t1,f1,frm,phse)
-//This function evaluates a chirp signal at time t.
-//Calling Sequence
-//y = chirp(t)
-//y = chirp(t, f0)
-//y = chirp(t, f0, t1)
-//y = chirp(t, f0, t1, f1)
-//y = chirp(t, f0, t1, f1, frm)
-//y = chirp(t, f0, t1, f1, frm, phse)
-//Parameters 
-//t: vector
-//f0:
-//t1:
-//f1:
-//frm: string value, takes in "linear", "quadratic", "logarithmic"
-//phse:
-//Description
-//This is an Octave function.
-//This function evaluates a chirp signal at time t. A chirp signal is a frequency swept cosine wave.
-//The first argument is a vector of times to evaluate the chirp signal, second argument is the frequency at t=0, third argument is time t1 and fourth argument is frequency at t1.
-//The fifth argument is the form which takes in values "linear", "quadratic" and "logarithmic", the sixth argument gives the phase shift at t=0.
-//Examples
-//chirp([4,3,2,1],4,5,0.9)
-//ans  =
-//           column 1 to 3
-//    0.9685832    0.2486899    0.0627905  
-//         column 4
-//  - 0.3681246  
- 
-funcprot(0);
-
-rhs = argn(2)
-if(rhs<1 | rhs>6)
-error("Wrong number of input arguments.")
-end
-	select(rhs)
-	case 1 then
-		y = callOctave("chirp",t)
-	case 2 then
-		y = callOctave("chirp",t,f0)
-	case 3 then
-		y = callOctave("chirp",t,f0,t1)
-	case 4 then
-		y = callOctave("chirp",t,f0,t1,f1)
-	case 5 then
-		//if(~(form == "linear" | form == "quadratic" | form == "logarithmic"))
-		//error("Chirp does not understand that form. Enter linear, quadratic or logarithmic.")
-		//else
-		y = callOctave("chirp",t,f0,t1,f1,frm)
-		//end
-	case 6 then
-		y = callOctave("chirp",t,f0,t1,f1,frm,phse)
-	end
+// 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:Sonu Sharma, RGIT Mumbai
+// Organization: FOSSEE, IIT Bombay
+// Email: toolbox@scilab.in
+
+function [y] = chirp(t,f0,t1,f1,form,phase)
+    //This function evaluates a chirp signal at time t.
+
+    //Calling Sequence
+    //y = chirp(t)
+    //y = chirp(t, f0)
+    //y = chirp(t, f0, t1)
+    //y = chirp(t, f0, t1, f1)
+    //y = chirp(t, f0, t1, f1, frm)
+    //y = chirp(t, f0, t1, f1, frm, phse)
+
+    //Parameters
+    //t:  a vector of times to evaluate the chirp signal
+    //f0: the frequency at t=0 [default value = 0 Hz]
+    //t1: some intermediate time [default value = 1 sec]
+    //f1: frequency at t1. [default value = 100 Hz]
+    //frm: string value, takes in "linear", "quadratic", "logarithmic" [default value = "linear"]
+    //phse: phase shift at t=0. [default value = 0]
+    //y: chirp signal value corresponding to t.
+
+    //Description
+    //This function evaluates a chirp signal at time t. A chirp signal is a frequency swept cosine wave.
+    //The first argument is a vector of times to evaluate the chirp signal, second argument is the frequency at t=0, third argument is time t1 and fourth argument is frequency at t1.
+    //The fifth argument is the form which takes in values "linear", "quadratic" and "logarithmic", the sixth argument gives the phase shift at t=0.
+
+    //Examples
+    //t = [4,3,2,1];
+    //f0 = 4;
+    //t1 = 5;
+    //f1 = 0.9;
+    //form = "quadratic";
+    //y = chirp(t, f0, t1, f1, form)
+    //Output :
+    // y  =
+    //
+    //  - 0.6112508    0.7459411  - 0.4854201    0.9664658
+
+    funcprot(0);
+    [nargout,nargin]=argn(0);
+
+    if nargin < 1 | nargin > 6
+        error("chirp: invalid number of inputs");
+    end
+    if nargin < 2, f0 = []; end
+    if nargin < 3, t1 = []; end
+    if nargin < 4, f1 = []; end
+    if nargin < 5, form = []; end
+    if nargin < 6, phase = []; end
+
+    if isempty(f0), f0 = 0; end
+    if isempty(t1), t1 = 1; end
+    if isempty(f1), f1 = 100; end
+    if isempty(form), form = "linear"; end
+    if isempty(phase), phase = 0; end
+
+    phase = 2*%pi*phase/360;
+
+    if (form== "linear")
+        a = %pi*(f1 - f0)/t1;
+        b = 2*%pi*f0;
+        y = cos(a*t.^2 + b*t + phase);
+    elseif (form== "quadratic")
+        a = (2/3*%pi*(f1-f0)/t1/t1);
+        b = 2*%pi*f0;
+        y = cos(a*t.^3 + b*t + phase);
+    elseif (form== "logarithmic")
+        a = 2*%pi*t1/log(f1-f0);
+        b = 2*%pi*f0;
+        x = (f1-f0)^(1/t1);
+        y = cos(a*x.^t + b*t + phase);
+    else
+        error(sprintf("chirp: chirp doesnt understand ''%s''",form));
+    end
 endfunction
-