ode45 returns NaN for a system of differential equations?

1 次查看（过去 30 天）
Evan
Evan 2014-2-22
编辑： Mischa Kim 2014-2-22
I am attempting to generate two vectors, tv and Yv, to plot a series of differential equations. Given my funciton:
function dydt=Tcells(t,y)
dydt(1,1)=(10 + 0.03*y(1)*(1-y(1)/t) - 0.02*y(1) - (2.4e-5)*y(4)*y(1));
dydt(2,1)=(2.4e-5)*y(4)*y(1) - 0.02*y(2) - (3e-3)*y(2);
dydt(3,1)=(3e-3)*y(2) - 0.24*y(3);
dydt(4,1)=1400*y(3) - 2.4e-5*y(4)*y(1) - 2.4*y(4);
and the following ode45 script entry:
[tv, Yv]=ode45('Tcells',[0 1500],[500, 0, 0, 1000]);
I cannot figure out why all entries of Yv, save the first row, return NaN as their values.
Any and all help is appreciated.

请先登录，再回答此问题。

采纳的回答

Mischa Kim
Mischa Kim 2014-2-22
编辑：Mischa Kim 2014-2-22
Evan, the issue is the term
(1-y(1)/t)
at t=0. If you set t0 for the integration time span slightly differently, such as
[tv, Yv] = ode45('Tcells',[0.1 1500],[500, 0, 0, 1000]); % 0.1 instead of 0.0
you should get it to work. Also, to improve readability and performance (especially for more complex, non-linear ODEs):
function dydt = Tcells(t,y)
y1 = y(1);
y2 = y(2);
y3 = y(3);
y4 = y(4);
dydt = [10 + 0.03*y1*(1-y1/t) - 0.02*y1 - (2.4e-5)*y4*y1; ...
(2.4e-5)*y4*y1 - 0.02*y2 - (3e-3)*y2; ...
(3e-3)*y2 - 0.24*y3; ...
1400*y3 - 2.4e-5*y4*y1 - 2.4*y4];
end

更多回答（0 个）

类别

在 Help Center 和 File Exchange 中查找有关 Ordinary Differential Equations 的更多信息

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by