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// 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
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