MATLAB: How to get the value for x and y in the 3D plot for a max z

find x and y value.

I have the following code.
%%
E=200e9; I=7.999e-5; K=-1/(E*I); x=[0:0.1:25]; vv=[];
for i=0:0.1:25
    B=[ 0 0 0 0 0 0 0 1 ;
        125/6 0 0 0 0 0 5 1 ;
        500/3 125/6 0 0 0 0 10 1 ;
        1125/2 500/3 125/6 0 0 0 15 1 ;
        4000/3 1125/2 500/3 125/6 0 0 20 1 ;
        15625/6 4000/3 1125/2 500/3 125/6 0 25 1 ;
        1 1 1 1 1 1 0 0 ;
        25 20 15 10 5 0 0 0 ];
    c=[0 ; (98100./6).*(max(5-i,0)).^3 ; (98100./6).*(max(10-i,0)).^3 ; (98100./6).*(max(15-i,0)).^3 ; (98100./6).*(max(20-i,0)).^3 ; (98100./6).*(max(25-i,0)).^3 ; 98100 ; 98100.*(25-i)];
    z=B\c;
    % The Values of all of the Reaction Forces and Integration Constants are as follows:
    Ra = z(1);
    Rb = z(2);
    Rc = z(3);
    Rd = z(4);
    Re = z(5);
    Rf = z(6);
    C1 = z(7);         % Integration Constand

    C2 = z(8);         % Integration Constand
    V=K.*(Ra.*((max(x,0)).^3)./6+Rb.*((max(x-5,0)).^3)./6+Rc.*((max(x-10,0)).^3)./6+Rd.*((max(x-15,0)).^3)./6+Re.*((max(x-20,0)).^3)./6-98100.*(((max(x-i,0))).^3)./6 + C1.*x + C2);
    vv=[vv;V];
end
p=[0:0.1:25];
% Generate coordinate pairs [X,P]=meshgrid(x,p); figure(100) surf(X,P,vv);
% % Evaluate function on grid
% Plot surface shading interp; hold on xlabel('Beam Length (m)') ylabel('Crane Position (m)') zlabel('Deflection (m)') hold off
[Zmax,Idx] = max(vv(:)) [ZmaxRow,ZmaxCol] = ind2sub(size(vv), Idx)
%%
I need the x and y value for a specific max z. How do I get it? I have the position in the matrix for the max z but not the value of x and y at that max z. then how doe you find 2 * max z values if your plot shows two values?
Please help me if you can?

Best Answer

clc; clear all ;
[X,Y,Z] = peaks(25) ;
[val,idx] = max(Z(:)) ;  % get maximum in Z 
x = X(idx) ;  % get x for zmax 
y = Y(idx) ;  % get y for zmax 
surf(X,Y,Z) ;
hold on
plot3(x,y,val,'*r') ;
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