two equal variable if condition

x=1:10:100;
y=1:10:100;
[x,y]=meshgrid(x,y);

for i=[x,y]
if  x (:,i) <= 52 && y (:,i) <= 52
     z= 0.00000512*x.^2+0.00000512*y.^2
elseif  x,y (:,i)> 77 
     z= 0.0000126*x.^2 + 0.0000126*y.^2
else
     z= -0.00000492*x.^2 - 0.00000492*y.^2
end
mesh(x,y,z)
end

Answer 1

[David Hill]

Not sure if this is what you are after or not. Your question was not clear.

[x,y]=meshgrid(1:10:100,1:10:100);
z=-0.00000492*x.^2 - 0.00000492*y.^2;
z(x<=52&y<=52)=0.00000512*x(x<=52&y<=52).^2+0.00000512*y(x<=52&y<=52).^2;
z(x>77&y>77)=0.0000126*x(x>77&y>77).^2 + 0.0000126*y(x>77&y>77).^2;\
mesh(x,y,z);

[manoj pandey]

Thanks David, it worked. I was tring to appy condition for Z matrix.

[Walter Roberson]

As a matter of style, I prefer to store the results of the test into a variable and use the variable as required. For example,

mask = x>77&y>77;
z(mask)=0.0000126*x(mask).^2 + 0.0000126*y(mask).^2;

This makes it more obvious that the same condition is being used in all cases, and reduces the risk of accidentally typing the condition different ways in different places. It would also be more efficient as it would not have to calculate the test multiple times.

There is a more obscure reason as well: in general, the evaluation of the test could have "side effects", and storing the results of the test into a variable ensures that a consistent version is used. For example, consider

z(x>77&y>randi(100))=0.0000126*x(x>77&y>randi(100)).^2 + 0.0000126*y(x>77&y>randi(100)).^2;

compared to

mask = x>77&y>randi(100);
z(mask)=0.0000126*x(mask).^2 + 0.0000126*y(mask).^2;