MATLAB: How to use quiver with equations in function

matlab functionodequiver

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!

Best Answer

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
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