peakdet

Peakdet
        [MAXTAB, MINTAB] = PEAKDET(V, DELTA) finds the local
        maxima and minima ("peaks") in the vector V.
        MAXTAB and MINTAB consists of two columns. Column 1
        contains indices in V, and column 2 the found values.
      
        With [MAXTAB, MINTAB] = PEAKDET(V, DELTA, X) the indices
        in MAXTAB and MINTAB are replaced with the corresponding
        X-values.

        A point is considered a maximum peak if it has the maximal
        value, and was preceded (to the left) by a value lower by
        DELTA.

0001 function [ maxtab,mintab ] = peakdet( v, delta,x )
0002 %Peakdet
0003 %        [MAXTAB, MINTAB] = PEAKDET(V, DELTA) finds the local
0004 %        maxima and minima ("peaks") in the vector V.
0005 %        MAXTAB and MINTAB consists of two columns. Column 1
0006 %        contains indices in V, and column 2 the found values.
0007 %
0008 %        With [MAXTAB, MINTAB] = PEAKDET(V, DELTA, X) the indices
0009 %        in MAXTAB and MINTAB are replaced with the corresponding
0010 %        X-values.
0011 %
0012 %        A point is considered a maximum peak if it has the maximal
0013 %        value, and was preceded (to the left) by a value lower by
0014 %        DELTA.
0015 
0016 % Eli Billauer, 3.4.05 (Explicitly not copyrighted).
0017 % This function is released to the public domain; Any use is allowe
0018 
0019 maxtab = [];
0020 mintab = [];
0021 
0022 v = v(:); % Just in case this wasn't a proper vector
0023 
0024 if nargin < 3
0025   x = (1:length(v))';
0026 else 
0027   x = x(:);
0028   if length(v)~= length(x)
0029     error('Input vectors v and x must have same length');
0030   end
0031 end
0032   
0033 if (length(delta(:)))>1
0034   error('Input argument DELTA must be a scalar');
0035 end
0036 
0037 if delta <= 0
0038   error('Input argument DELTA must be positive');
0039 end
0040 
0041 mn = Inf; mx = -Inf;
0042 mnpos = NaN; mxpos = NaN;
0043 
0044 lookformax = 1;
0045 
0046 for i=1:length(v)
0047   this = v(i);
0048   if this > mx, mx = this; mxpos = x(i); end
0049   if this < mn, mn = this; mnpos = x(i); end
0050   
0051   if lookformax
0052     if this < mx-delta
0053       maxtab = [maxtab ; mxpos mx];
0054       mn = this; mnpos = x(i);
0055       lookformax = 0;
0056     end  
0057   else
0058     if this > mn+delta
0059       mintab = [mintab ; mnpos mn];
0060       mx = this; mxpos = x(i);
0061       lookformax = 1;
0062     end
0063   end
0064 end