function P=findpeaksplot(x,y,SlopeThreshold,AmpThreshold,smoothwidth,peakgroup,smoothtype) % function % P=findpeaksplot(x,y,SlopeThreshold,AmpThreshold,smoothwidth,peakgroup,... % smoothtype) Function to locate and plot the positive peaks in a noisy x-y % time series data set. Detects peaks by looking for downward % zero-crossings in the first derivative that exceed SlopeThreshold. % Returns list (P) containing peak number and position, % height, width, and area of each peak. Arguments "slopeThreshold", % "ampThreshold" and "smoothwidth" control peak sensitivity. % Higher values will neglect smaller features. "Smoothwidth" is % the width of the smooth applied before peak detection; larger % values ignore narrow peaks. If smoothwidth=0, no smoothing % is performed. "Peakgroup" is the number points around the top % part of the peak that are taken for measurement. If Peakgroup=0 % the local maximum is takes as the peak height and position. % The argument "smoothtype" determines the smooth algorithm: % If smoothtype=1, rectangular (sliding-average or boxcar) % If smoothtype=2, triangular (2 passes of sliding-average) % If smoothtype=3, pseudo-Gaussian (3 passes of sliding-average) % See http://terpconnect.umd.edu/~toh/spectrum/Smoothing.html and % http://terpconnect.umd.edu/~toh/spectrum/PeakFindingandMeasurement.htm % T. C. O'Haver, 1995. Version 6.1, Last revised May, 2016 % % Examples: % findpeaksplot(0:.01:2,humps(0:.01:2),0,-1,5,5) % x=[0:.01:50];findpeaksplot(x,cos(x),0,-1,5,5) % x=[0:.01:5]';y=x.*sin(x.^2).^2;P=findpeaksplot(x,y,0,-1,5,5) % % Related functions: % findvalleys.m, findpeaksL.m, findpeaksb.m, findpeaks.m, peakstats.m, % findpeaksnr.m, findpeaksGSS.m, findpeaksLSS.m, findpeaksfit.m. if nargin~=7;smoothtype=1;end % smoothtype=1 if not specified in argument if smoothtype>3;smoothtype=3;end if smoothtype<1;smoothtype=1;end smoothwidth=round(smoothwidth); peakgroup=round(peakgroup); if smoothwidth>1, d=fastsmooth(deriv(y),smoothwidth,smoothtype); else d=y; end n=round(peakgroup/2+1); P=[0 0 0 0 0]; vectorlength=length(y); peak=1; for j=2*round(smoothwidth/2)-1:length(y)-smoothwidth, if sign(d(j)) > sign (d(j+1)), % Detects zero-crossing if d(j)-d(j+1) > SlopeThreshold, % if slope of derivative is larger than SlopeThreshold if y(j) > AmpThreshold, % if height of peak is larger than AmpThreshold xx=zeros(size(peakgroup));yy=zeros(size(peakgroup)); for k=1:peakgroup, % Create sub-group of points near peak groupindex=j+k-n+1; if groupindex<1, groupindex=1;end if groupindex>vectorlength, groupindex=vectorlength;end xx(k)=x(groupindex);yy(k)=y(groupindex); end if peakgroup>3, [Height, Position, Width]=gaussfit(xx,yy); PeakX=real(Position); % Compute peak position and height of fitted parabola PeakY=real(Height); MeasuredWidth=real(Width); % if the peak is too narrow for least-squares technique to work % well, just use the max value of y in the sub-group of points near peak. else PeakY=max(yy); pindex=val2ind(yy,PeakY); PeakX=xx(pindex(1)); MeasuredWidth=0; end % Construct matrix P. One row for each peak % detected, containing the peak number, peak % position (x-value) and peak height (y-value). % If peak measurements fails and results in NaN, skip this % peak if isnan(PeakX) || isnan(PeakY), % Skip this peak else % Otherwise count this as a valid peak P(peak,:) = [round(peak) PeakX PeakY MeasuredWidth 1.0646.*PeakY*MeasuredWidth]; peak=peak+1; % Move on to next peak end end end end end plot(x,y) text(P(:,2),P(:,3),num2str(P(:,1))) % ---------------------------------------------------------------------- function [index,closestval]=val2ind(x,val) % Returns the index and the value of the element of vector x that is closest to val % If more than one element is equally close, returns vectors of indicies and values % Tom O'Haver (toh@umd.edu) October 2006 % Examples: If x=[1 2 4 3 5 9 6 4 5 3 1], then val2ind(x,6)=7 and val2ind(x,5.1)=[5 9] % [indices values]=val2ind(x,3.3) returns indices = [4 10] and values = [3 3] dif=abs(x-val); index=find((dif-min(dif))==0); closestval=x(index); function d=deriv(a) % First derivative of vector using 2-point central difference. % T. C. O'Haver, 1988. n=length(a); d(1)=a(2)-a(1); d(n)=a(n)-a(n-1); for j = 2:n-1; d(j)=(a(j+1)-a(j-1)) ./ 2; end function SmoothY=fastsmooth(Y,w,type,ends) % fastbsmooth(Y,w,type,ends) smooths vector Y with smooth % of width w. Version 2.0, May 2008. % The argument "type" determines the smooth type: % If type=1, rectangular (sliding-average or boxcar) % If type=2, triangular (2 passes of sliding-average) % If type=3, pseudo-Gaussian (3 passes of sliding-average) % The argument "ends" controls how the "ends" of the signal % (the first w/2 points and the last w/2 points) are handled. % If ends=0, the ends are zero. (In this mode the elapsed % time is independent of the smooth width). The fastest. % If ends=1, the ends are smoothed with progressively % smaller smooths the closer to the end. (In this mode the % elapsed time increases with increasing smooth widths). % fastsmooth(Y,w,type) smooths with ends=0. % fastsmooth(Y,w) smooths with type=1 and ends=0. % Example: % fastsmooth([1 1 1 10 10 10 1 1 1 1],3)= [0 1 4 7 10 7 4 1 1 0] % fastsmooth([1 1 1 10 10 10 1 1 1 1],3,1,1)= [1 1 4 7 10 7 4 1 1 1] % T. C. O'Haver, May, 2008. if nargin==2, ends=0; type=1; end if nargin==3, ends=0; end switch type case 1 SmoothY=sa(Y,w,ends); case 2 SmoothY=sa(sa(Y,w,ends),w,ends); case 3 SmoothY=sa(sa(sa(Y,w,ends),w,ends),w,ends); end function SmoothY=sa(Y,smoothwidth,ends) w=round(smoothwidth); SumPoints=sum(Y(1:w)); s=zeros(size(Y)); halfw=round(w/2); L=length(Y); for k=1:L-w, s(k+halfw-1)=SumPoints; SumPoints=SumPoints-Y(k); SumPoints=SumPoints+Y(k+w); end s(k+halfw)=sum(Y(L-w+1:L)); SmoothY=s./w; % Taper the ends of the signal if ends=1. if ends==1, startpoint=(smoothwidth + 1)/2; SmoothY(1)=(Y(1)+Y(2))./2; for k=2:startpoint, SmoothY(k)=mean(Y(1:(2*k-1))); SmoothY(L-k+1)=mean(Y(L-2*k+2:L)); end SmoothY(L)=(Y(L)+Y(L-1))./2; end % ---------------------------------------------------------------------- function [Height, Position, Width]=gaussfit(x,y) % Converts y-axis to a log scale, fits a parabola % (quadratic) to the (x,ln(y)) data, then calculates % the position, width, and height of the % Gaussian from the three coefficients of the % quadratic fit. This is accurate only if the data have % no baseline offset (that is, trends to zero far off the % peak) and if there are no zeros or negative values in y. % % Example 1: Simplest Gaussian data set % [Height, Position, Width]=gaussfit([1 2 3],[1 2 1]) % returns Height = 2, Position = 2, Width = 2 % % Example 2: best fit to synthetic noisy Gaussian % x=50:150;y=100.*gaussian(x,100,100)+10.*randn(size(x)); % [Height,Position,Width]=gaussfit(x,y) % returns [Height,Position,Width] clustered around 100,100,100. % % Example 3: plots data set as points and best-fit Gaussian as line % x=[1 2 3 4 5];y=[1 2 2.5 2 1]; % [Height,Position,Width]=gaussfit(x,y); % plot(x,y,'o',linspace(0,8),Height.*gaussian(linspace(0,8),Position,Width)) % Copyright (c) 2012, Thomas C. O'Haver maxy=max(y); for p=1:length(y), if y(p)<(maxy/100),y(p)=maxy/100;end end % for p=1:length(y), logyyy=log(abs(y)); [coef,S,MU]=polyfit(x,logyyy,2); c1=coef(3);c2=coef(2);c3=coef(1); % Compute peak position and height or fitted parabola Position=-((MU(2).*c2/(2*c3))-MU(1)); Height=exp(c1-c3*(c2/(2*c3))^2); Width=norm(MU(2).*2.35703/(sqrt(2)*sqrt(-1*c3)));