MATLAB: How to find the maximum value

double y-axismaximum

Below is a 3D graph.
   T=600:1:850;
    t=0.2:0.1:20;
    [tm,Tm] = meshgrid(t, T);
    k1 = 10^7.*exp(-12700./Tm);
    k2 = 5*10^4.*exp(-10800./Tm);
    k3 = 7*10^7.*exp(-15000./Tm);
    Y_B = (k1.*tm)./(((k2.*tm)+1).*(1+(tm.*(k1+k3))));
    mesh(t,T,Y_B)
    view(40, 45)
    grid on
How do I find the maximum value of Y_B for t=0.2:0.1:20 over the range of T from 600 to 850 and plots on a double y-axis graph the value of T and Y_Bmax with t?

Best Answer

   t = 0.2:0.1:20;
   T = 600:50:850;
   for i = 1:numel(T)
      k1 = 1e7 .* exp(-12700 ./ T(i));
      k2 = 5e4 .* exp(-10800 ./ T(i));
      k3 = 7e7 .* exp(-15000 ./ T(i));
      for j = 1:numel(t)
         Y_B(i,j) = (k1.*t(j)) ./ (((k2.*t(j))+1).*(1+(t(j).*(k1+k3))));
         % Prefer:
         % Y_B(i,j) = k1 .* t(j) ./ ((k2 .* t(j) + 1) .* (1 + t(j) .* (k1 + k3)));
      end
  end
  plot(t, max(Y_B, [], 1), '.-');
k1, k2, k3 are not changed inside the inner loop, so move them to the outer one. I would not overdo it with the parentheses.
By the way, you can even omit the loops:
t   = 0.2:0.1:20;
T   = (600:50:850).';
k1  = 1e7 .* exp(-12700 ./ T);
k2  = 5e4 .* exp(-10800 ./ T);
k3  = 7e7 .* exp(-15000 ./ T);
Y_B = k1 .* t ./ ((k2 .* t + 1) .* (1 + t .* (k1 + k3)));  % >= R2016
plot(t, max(Y_B, [], 1), '.-');
This uses auto expanding, which was introduced in Matlab R2016b. Your meshgrid approach was fine also, while the loops suggested by Birdman have no advantage here.
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