author | A.M. Thurnherr <athurnherr@yahoo.com> |
Tue, 29 Jun 2021 09:14:43 -0400 | |
changeset 23 | e83393696a24 |
parent 0 | 0a450563f904 |
permissions | -rw-r--r-- |
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0a450563f904
VIX_6: first version for Mercurial release
A.M. Thurnherr <ant@ldeo.columbia.edu>
parents:
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1 |
function [xout,yout,imaxout] = localmax2(X,Y); |
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VIX_6: first version for Mercurial release
A.M. Thurnherr <ant@ldeo.columbia.edu>
parents:
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% LOCALMAX2 - find local maxima by parabola fitting |
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% [xm,ym]=LOCALMAX2(x,y) returns maxima for every triplet of points (along 1st dim). |
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% xm(i,j)=NaN means that there is no local maximum of y(:,j)=F{x(:,j)} between x(i,j) and x(i+2,j) |
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VIX_6: first version for Mercurial release
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parents:
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% x may be the same size as y or as y(:,1) |
0a450563f904
VIX_6: first version for Mercurial release
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parents:
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% added to find the three highest points of array |
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VIX_6: first version for Mercurial release
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|
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% August 2001, ashcherbina@ucsd.edu |
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VIX_6: first version for Mercurial release
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% April 2004, Visbeck visbeck@ldeo.columbia.edu |
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parents:
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|
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VIX_6: first version for Mercurial release
A.M. Thurnherr <ant@ldeo.columbia.edu>
parents:
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% fix array sizes |
0a450563f904
VIX_6: first version for Mercurial release
A.M. Thurnherr <ant@ldeo.columbia.edu>
parents:
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if size(X,1)==size(Y,1) & size(X,2)==1 |
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X=repmat(X,1,size(Y,2)); |
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end |
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|
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VIX_6: first version for Mercurial release
A.M. Thurnherr <ant@ldeo.columbia.edu>
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16 |
% find maximum |
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[dum,imax]=max(Y); |
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xout=imax+nan; |
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yout=imax+nan; |
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imaxout=imax+nan; |
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|
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% select valid indices for fit |
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iok=find(imax>1 & imax<(size(Y,1))); |
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|
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% restrict to valid values |
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imaxout(iok)=imax(iok); |
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imaxn=imax(iok); |
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|
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if length(iok)>0 |
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disp([' localmax2: found ',int2str(length(iok)),' valid values']) |
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else |
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disp([' localmax2 found no valid values']) |
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return |
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end |
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|
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for i=1:length(imaxn) |
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j=iok(i); |
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x1(i)=X(imaxn(i)-1,j); |
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x2(i)=X(imaxn(i),j); |
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x3(i)=X(imaxn(i)+1,j); |
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y1(i)=Y(imaxn(i)-1,j); |
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y2(i)=Y(imaxn(i),j); |
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parents:
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y3(i)=Y(imaxn(i)+1,j); |
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end |
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% compute fit to parabola |
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a=(x3.*y2+x1.*y3-x1.*y2-y3.*x2-y1.*x3+y1.*x2)./... |
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(x3.*x2.^2-x1.*x2.^2+x1.*x3.^2-x1.^2.*x3+x1.^2.*x2-x3.^2.*x2); |
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b=-(-x2.^2.*y3+x2.^2.*y1-y2.*x1.^2+y3.*x1.^2-x3.^2.*y1+y2.*x3.^2)./... |
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((-x3+x2).*(x2.*x3-x2.*x1+x1.^2-x3.*x1) ); |
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c=(x2.^2.*y1.*x3-x2.^2.*x1.*y3-x3.^2.*y1.*x2+... |
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y3.*x1.^2.*x2+x3.^2.*x1.*y2-y2.*x1.^2.*x3)./... |
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((-x3+x2).*(x2.*x3-x2.*x1+x1.^2-x3.*x1)); |
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|
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% check for maximum in range |
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xn=x1+nan; |
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ii=find(a<0); |
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xn(ii)=-b(ii)./a(ii)/2; |
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|
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% compute max taget strength if desired |
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xout(iok)=xn; |
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if nargout>1 |
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yn=xn.^2.*a+xn.*b+c; |
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yout(iok)=yn; |
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end |
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A.M. Thurnherr <ant@ldeo.columbia.edu>
parents:
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