[37] | 1 | function [lmval,indd]=lmax(xx,filt)
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| 2 | %LMAX [lmval, indd]=lmax(xx,filt). Find local maxima in vector XX,where
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| 3 | % LMVAL is the output vector with maxima values, INDD is the
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| 4 | % corresponding indexes, FILT is the number of passes of the small
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| 5 | % running average filter in order to get rid of small peaks. Default
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| 6 | % value FILT =0 (no filtering). FILT in the range from 1 to 3 is
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| 7 | % usially sufficient to remove most of a small peaks
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| 8 | % For example:
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| 9 | % xx=0:0.01:35; y=sin(xx) + cos(xx ./3);
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| 10 | % plot(xx,y); grid; hold on;
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| 11 | % [b,a]=lmax(y,2)
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| 12 | % plot(xx(a),y(a),'r+')
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| 13 | % see also LMIN, MAX, MIN
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| 14 |
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| 15 | %**************************************************|
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| 16 | % Serge Koptenko, Guigne International Ltd., |
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| 17 | % phone (709)895-3819, fax (709)895-3822 |
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| 18 | %--------------06/03/97----------------------------|
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| 19 |
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| 20 | x=xx;
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| 21 | len_x = length(x);
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| 22 | fltr=[1 1 1]/3;
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| 23 | if nargin <2, filt=0;
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| 24 | else
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| 25 | x1=x(1); x2=x(len_x);
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| 26 | for jj=1:filt,
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| 27 | c=conv(fltr,x);
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| 28 | x=c(2:len_x+1);
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| 29 | x(1)=x1;
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| 30 | x(len_x)=x2;
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| 31 | end
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| 32 | end
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| 33 | lmval=[]; indd=[];
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| 34 | i=2; % start at second data point in time series
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| 35 | while i < len_x-1,
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| 36 | if x(i) > x(i-1)
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| 37 | if x(i) > x(i+1) % definite max
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| 38 | lmval =[lmval x(i)];
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| 39 | indd = [ indd i];
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| 40 | elseif x(i)==x(i+1)&x(i)==x(i+2) % 'long' flat spot
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| 41 | %lmval =[lmval x(i)]; %1 comment these two lines for strict case
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| 42 | %indd = [ indd i]; %2 when only definite max included
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| 43 | i = i + 2; % skip 2 points
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| 44 | elseif x(i)==x(i+1) % 'short' flat spot
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| 45 | %lmval =[lmval x(i)]; %1 comment these two lines for strict case
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| 46 | %indd = [ indd i]; %2 when only definite max included
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| 47 | i = i + 1; % skip one point
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| 48 | end
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| 49 | end
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| 50 | i = i + 1;
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| 51 | end
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| 52 | if filt>0 & ~isempty(indd),
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| 53 | if (indd(1)<= 3)|(indd(length(indd))+2>length(xx)),
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| 54 | rng=1; %check if index too close to the edge
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| 55 | else rng=2;
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| 56 | end
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| 57 | for ii=1:length(indd), % Find the real maximum value
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| 58 | [val(ii) iind(ii)] = max(xx(indd(ii) -rng:indd(ii) +rng));
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| 59 | iind(ii)=indd(ii) + iind(ii) -rng-1;
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| 60 | end
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| 61 | indd=iind; lmval=val;
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| 62 | else
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| 63 | end
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| 64 |
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| 65 |
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