V_ZEROCROS finds the zeros crossings in a signal [T,S]=(Y,M,X)
Inputs: y = input waveform
m = mode string containing:
'p' - positive crossings only
'n' - negative crossings only
'b' - both (default)
'r' - round to sample values
x = x-axis values corresponding to y [default 1:length(y)]
Outputs: t = x-axis positions of zero crossings
s = estimated slope of y at the zero crossing
This routine uses linear interpolation to estimate the position of a zero crossing
A zero crossing occurs between y(n) and y(n+1) iff (y(n)>=0) ~= (y(n+1)>=0)0001 function [t,s]=v_zerocros(y,m,x) 0002 %V_ZEROCROS finds the zeros crossings in a signal [T,S]=(Y,M,X) 0003 % Inputs: y = input waveform 0004 % m = mode string containing: 0005 % 'p' - positive crossings only 0006 % 'n' - negative crossings only 0007 % 'b' - both (default) 0008 % 'r' - round to sample values 0009 % x = x-axis values corresponding to y [default 1:length(y)] 0010 % 0011 % Outputs: t = x-axis positions of zero crossings 0012 % s = estimated slope of y at the zero crossing 0013 % 0014 % This routine uses linear interpolation to estimate the position of a zero crossing 0015 % A zero crossing occurs between y(n) and y(n+1) iff (y(n)>=0) ~= (y(n+1)>=0) 0016 0017 % Example: y=sin(2*pi*(0:1000)/200); y(1:100:1001)=0; v_zerocros(y); 0018 % Note that we get a zero crossing at the end but not at the start. 0019 0020 % Copyright (C) Mike Brookes 2003-2015 0021 % Version: $Id: v_zerocros.m 10865 2018-09-21 17:22:45Z dmb $ 0022 % 0023 % VOICEBOX is a MATLAB toolbox for speech processing. 0024 % Home page: http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/voicebox.html 0025 % 0026 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 0027 % This program is free software; you can redistribute it and/or modify 0028 % it under the terms of the GNU General Public License as published by 0029 % the Free Software Foundation; either version 2 of the License, or 0030 % (at your option) any later version. 0031 % 0032 % This program is distributed in the hope that it will be useful, 0033 % but WITHOUT ANY WARRANTY; without even the implied warranty of 0034 % MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 0035 % GNU General Public License for more details. 0036 % 0037 % You can obtain a copy of the GNU General Public License from 0038 % http://www.gnu.org/copyleft/gpl.html or by writing to 0039 % Free Software Foundation, Inc.,675 Mass Ave, Cambridge, MA 02139, USA. 0040 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 0041 0042 if nargin<2 || ~numel(m) 0043 m='b'; 0044 end 0045 s=y>=0; 0046 k=s(2:end)-s(1:end-1); 0047 if any(m=='p') 0048 f=find(k>0); 0049 elseif any(m=='n') 0050 f=find(k<0); 0051 else 0052 f=find(k~=0); 0053 end 0054 s=y(f+1)-y(f); 0055 t=f-y(f)./s; 0056 if any(m=='r') 0057 t=round(t); 0058 end 0059 if nargin>2 0060 tf=t-f; % fractional sample 0061 t=x(f).*(1-tf)+x(f+1).*tf; 0062 s=s./(x(f+1)-x(f)); 0063 end 0064 if ~nargout 0065 n=length(y); 0066 if nargin>2 0067 plot(x,y,'-b',t,zeros(length(t),1),'or'); 0068 else 0069 plot(1:n,y,'-b',t,zeros(length(t),1),'or'); 0070 end 0071 v_axisenlarge([-1 -1.05]); 0072 end