Using a meshgrid or vector inside all function

Hi

I am trying to run an optimization on a 2 variable f(x,y) function inside a region. This region is defined by a mesh-grid of points. Since this grid of points is not changed in every iteration of the optimization, I like to define this mesh grid before the optimization commands and outside my cost function so that the cost function has only unknown variables as input while inside it I can used the grid variable. I would like to do this:

global a a=[1 2 3] %the grid data here

and then the cost function of the optimization algorithm is like this: function out=costfun(x) out=x(1)*a(1)+x(1)*a(1)+...

but it does not work. every time the function is called, the global a variable is now know to it. I should give this grid to the function as input. what can I do about it? Thanks in advance

Answer 1

[Honglei Chen]

You need to put

global a

in your cost function too. See the example in

https://www.mathworks.com/help/matlab/ref/global.html

HTH

[hossein]

Thanks for the reply. Since this function will be called multiple times, does your solution solve this problem? I mean if every time inside the function a mesh grid is defined, it is not what I wanted. I want for Matlab to take this mesh-grid matrix one time and used it in this function for many iterations without losing processing time and redefining the mesh-grid again.

[Honglei Chen]

I'm trying to illustrate how global should be used in MATLAB. For a function to see the global variable, you need to add the global declaration in the function. It's a declaration, you don't need to redefine it.

[hossein]

Oh. sorry. Now I got what you meant. 1- define the grid before the function as a global var and assign values to it. 2-call the function without the grid as the input. 3-use "global a" command inside the function to declare the previously defined a.

I tested it and it worked. Thanks!