How to use quiver with equations in function?

I have defined several functions with equations like

function dZ = ODE(~,z)
 x  = z(1);
 y  = z(2);
 dZ = [x+y;...   
       4*x-2*y]; 
end

These functions are used by other functions for solving etc. Now I want to do plotting with quiver but I don't figure out how to pass a function with equations as a parameter to quiver. It should look like this:

odehandle = str2func('ODE');
plot_vectorfield(odehandle);

function plot_vectorfield(odehandle)
   [x,y]=meshgrid(-10:1:10,-10:1:10);
   [dx,dy]=odehandle; %does not work!
   quiver(x,y,dx,dy);
end

So the problem is obviously how to pass the u,v parameter to quiver. I would also like to know how to handle function defined equation systems with 3 equations with quiver. Thanks a lot!

Answer 1

[Walter Roberson]

Replace

   [dx,dy]=odehandle; %does not work!

with

   temp = arrayfun(@(X, Y) odehandle([],[X,Y]), x, y, 'uniform', 0);
   dx = cellfun(@(C) C(1), temp);
   dy = cellfun(@(C) C(2), temp);

This is for the special case that the ODE is a function of two variables and the first derivatives apear as the first two elements of the output vector.

The 3D equivalent would be something like,

function plot_vectorfield(odehandle)
   [x, y, z]=meshgrid(-10:1:10, -10:1:10, -10:1:10);
   temp = arrayfun(@(X, Y, Z) odehandle([],[X,Y,Z]), x, y, z, 'uniform', 0);
   dx = cellfun(@(C) C(1), temp);
   dy = cellfun(@(C) C(2), temp);
   dz = cellfun(@(C) C(3), temp);
   quiver3(x, y, z, dx, dy, dz);
end

[Sam Finch]

Thanks a lot, works like a charm.