How to draw a 3D plot of a function in form y=f(X) and X is an array [X(1),X(2)] ?

Hi every body i need to draw a function in form :

    function F_cost= objfun(X)

     F_cost=(cos(X(1)*X(2)));

 I cant use fplot or ezsurf and i don't know why !!
for example ezsurf (objfun) or ezplot(objfun,[-3  3  -3  3]) doesn't work !!
Can any body help me plz !?

Bests Sadeg

Answer 1

[Mischa Kim]

Sadeg, use something like

 [X,Y] = meshgrid(0:0.1:1);
 Z = sin(X).*cos(3*Y).^2;
 surf(X,Y,Z)

[Mischa Kim]

I see. In the MATLAB command window use

 x = linspace(0,10,20);
 y = linspace(-5,5,20);
 F_cost= objfun([x' y'])

to execute

 function F_cost= objfun(X)
 [X1, X2] = meshgrid(X(:,1),X(:,2))
 F_cost   = cos(X1).*X2;
 surf(F_cost,X1,X2) 
 end

[ss]

Thanks. It works very well but, is there any alternative method that lets us do the same but without any change in function definition code. i mean :

function F_cost= objfun(X)
     F_cost=(cos(X(1)*X(2)));

[Mischa Kim]

There is no feasible alternative. The problem is

 F_cost=(cos(X(1)*X(2)));

which in this form takes two scalars to compute F_cost, which is also a scalar. With the solution I proposed you create n-by-m matrices to compute F_cost for all data points which is readily available for plotting. You could wrap your function in for-loops to compute each point individually, but that's everything but efficient. Especially for large matrices.

[ss]

Thanks

Answer 2

[ss]

Hi Mischa, thanks for your answer.Actually i cant change the function format at all. In fact its a part of a developing software so the format of functions are fixed by protocols. Consider there is 100s of two variable functions in form :

function F_cost= objfun(X)
     F_cost=(cos(X(1)*X(2)));

And we want to 3Dplot them, do you have any idea ?

[Mischa Kim]

See answer above. Please post follow-up questions and comments as comments, not questions.