MATLAB: Find a local max and local min of a surface with noise

maxminnoisesurface

I got the matrix above How can I find de MAXIMUM & MINIMUM locals and put the X,Y coodinate into a vector X and a vector Y and when i plot X vs Y o got the dots representating the maximum and minumum values with different color for max and min ps. remember to consider the noise
A=[0.5000 -0.2668 -0.4606 -0.0866 -0.1433 -0.2063 0.0020 -0.0684 0.0824 0.0618; -0.0700 -0.1001 -0.6211 -2.0000 -0.6901 -0.5352 -0.5370 0.6527 -0.4742 -0.2398; -0.0159 0.1090 0.0902 -0.3513 -0.5579 -0.2559 -0.1088 0.2090 -0.1592 0.0290; 0.3378 0.3437 0.4101 0.4995 0.3286 0.1963 0.0434 0.1998 0.2853 0.3430; 0.3673 0.3320 0.2836 0.3189 0.3596 0.1729 0.0493 0.2758 0.2314 0.3171; -0.7621 -0.5151 -0.3759 -0.1816 0.1758 0.0306 -0.4316 0.1782 -3.0051 -1.9493; -0.0107 -0.1784 -0.0642 -0.1268 -0.0137 0.0840 -0.1945 0.0944 -0.1449 -0.0296; 0.2212 0.1060 0.0321 3.0020 0.1965 -0.0060 0.0472 0.1958 0.1850 0.3266; 0.1410 0.2704 0.1225 0.2163 0.0337 0.1676 0.1012 0.1511 0.1105 0.3585; 0.1301 0.2741 0.0495 0.0251 0.1299 0.2433 0.0284 0.0727 0.1462 0.1443 ;]

Best Answer

  • I use a function extrema2 to do that and works here is the link http://www.mathworks.com/matlabcentral/fileexchange/12275-extrema-m-extrema2-m/content/extrema/extrema2.m and the code I use
    z=crop;
    [zmax,imax,zmin,imin] = extrema2(z,1);
    [m,n]=size(crop);
    y=1:m;
    x=1:n;
    [x,y]=meshgrid(x,y);
    crop(crop<=10)=nan
    figure
    hold on
    plot3(x(imax),y(imax),zmax,'bo',x(imin),y(imin),zmin,'ro')
    for i = 1:length(zmax)
    text(x(imax(i)),y(imax(i)),zmax(i),[' ' num2str(zmax(i))])
    end
    for i = 1:length(zmin)
    text(x(imin(i)),y(imin(i)),zmin(i),[' ' num2str(zmin(i))])
    end
    hold off
    hold on
    surf(crop)