Question

I want to know what is wrong with this code, and how to fix it please. i keep getting

Error using contour (line 48)
Z must be at least a 2x2 matrix.

Error in Projectrevised (line 42)
curve= contour(b,FOS1,h,'ShowText','on');

%% Constants
w = 450000;
l = 10;
n = 6;
SOM = 505000000;
max = 10;
min = 2;
diff = (max-min)/n;
FOS1 = zeros(n,n);
FOS2 = zeros(n,n);
i = 1;
j = 1;
Vm = (w*l)/2;

%% FOS@different base&height values

for b = min:diff:max
for h = min:diff:max
c = (h/2);
density=8000;
V=b*h*l;
mass=density*V;
Mmax = ((w*l^2)/8)*c;
I = (b*h^3)/12;
Bm = (Mmax*c)/I;
Tmax=(3*Vm)/2*(b*h);
Stressmax=(Mmax*c)/I;
FOS1(i,j) = (SOM/Tmax);
FOS2(i,j) = (SOM/Stressmax);
j = j+1;   
end
i = i+1;
end

%% Plotting
[B,H]=meshgrid(b,h);
FOS1(i,j) = (SOM/Tmax);
curve= contour(b,FOS1,h,'ShowText','on');
hold on
title('Beam Design')
xlabel('Base (meters)')
ylabel('Height (meters)')
close all
clear plot

Answer 1

If you are plotting a contour plot and plotting z against x and y, then z needs to be a matrix and not a 1 D array.

You are using h to be plotted on z axis, which is an array. However, i see you have converted array h to a matrix H, using meshgrid. So instead of using h, use H.

The command should be

curve= contour(b,FOS1,H,'ShowText','on');