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From: Marton Buda on 1 Apr 2010 14:20
Hey,

I'd like to plot velocity vectors for a set of ode's however the implementation makes me confused. I had a look at the following simple example:

tspan = [0 10];

yazero = [1; 1]; ybzero = [-5; 2] ; yczero = [5; -2];

[ta, ya] = ode45(@pend, tspan, yazero);
[tb, yb] = ode45(@pend, tspan, ybzero);
[tc, yc] = ode45(@pend, tspan, yczero);

[y1,y2] = meshgrid(-5:.5:5,-3:.5:3);
Dy1Dt = y2; Dy2Dt = -sin(y1);
quiver (y1,y2, Dy1Dt, Dy2Dt)
-----function---

function yprime = pend(t,y)


yprime = [y(2); -sin(y(1))];


--------------------

In my case the function file is slightly more complicated:


function dydt = cact(t, y)

dydt = zeros(size(y));

ea = 1.58;
eb = 0.079;
d = 15;
p = 50;

A = y(1);
B = y(2);

dydt(1) = d*(ea*((1+p*A^2)/(1+A^2+B^2))-A);

dydt(2) = d*eb*((1+p*A^2)/(1+A^2))-B;


If i simply put the expression into the code nothing is going to happen apart from getting a plane with the determined grid. Anyone has an idea how set of equations can be used with the command 'quiver'?

Cheers,

M.
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