清空筛选条件
清空筛选条件

How to plot nullclines with differential equations

48 次查看（过去 30 天）
Zachary David
Zachary David 2021-10-4
回答： Star Strider 2021-10-4
Im trying to plot nullclines on top of a mesh grid then use ode 45
i cant seem to get the nullclines on their though after googling for hours. This is my code:
x1min = -1; x1max = 6; x2min = -1; x2max = 6;
x1step = 0.3; x2step = 0.3;
[x1, x2] = meshgrid(x1min:x1step:x1max, x2min:x2step:x2max);
a = 1.5;
b=1.1;
g=2.5;
d=1.4;
dx1 = -a*x1+b*x1*x2;
dx2 = g*x2-d*x1*x2;
nullX1= -a + b.*x2;
nullX2= g - d.*x1;
quiver(x1, x2, dx1,dx2,'AutoScaleFactor',0.5)
axis([x1min x1max x2min x2max])
xlabel('$x1$','Interpreter','latex')
ylabel('$x2$','Interpreter','latex')
title('Vector field example','Interpreter','latex')
x=0:0.5:30;
plot(x,nullX1,'r-')
hold on
plot(x,nullX2,'k-')
hold on
*****It keeps telling my my vectors must be the same length, so not sure if im using the wrong parameters.
Thanks!

请先登录，再回答此问题。

采纳的回答

Star Strider
Star Strider 2021-10-4
Ran in:
Work-around —
x = linspace(0, 30, size(nullX1,1)); % Use 'linspace' To Create Correct Length 'x'
x1min = -1; x1max = 6; x2min = -1; x2max = 6;
x1step = 0.3; x2step = 0.3;
[x1, x2] = meshgrid(x1min:x1step:x1max, x2min:x2step:x2max);
a = 1.5;
b=1.1;
g=2.5;
d=1.4;
dx1 = -a*x1+b*x1*x2;
dx2 = g*x2-d*x1*x2;
nullX1= -a + b.*x2
nullX1 = 24×24
-2.6000 -2.6000 -2.6000 -2.6000 -2.6000 -2.6000 -2.6000 -2.6000 -2.6000 -2.6000 -2.6000 -2.6000 -2.6000 -2.6000 -2.6000 -2.6000 -2.6000 -2.6000 -2.6000 -2.6000 -2.6000 -2.6000 -2.6000 -2.6000 -2.2700 -2.2700 -2.2700 -2.2700 -2.2700 -2.2700 -2.2700 -2.2700 -2.2700 -2.2700 -2.2700 -2.2700 -2.2700 -2.2700 -2.2700 -2.2700 -2.2700 -2.2700 -2.2700 -2.2700 -2.2700 -2.2700 -2.2700 -2.2700 -1.9400 -1.9400 -1.9400 -1.9400 -1.9400 -1.9400 -1.9400 -1.9400 -1.9400 -1.9400 -1.9400 -1.9400 -1.9400 -1.9400 -1.9400 -1.9400 -1.9400 -1.9400 -1.9400 -1.9400 -1.9400 -1.9400 -1.9400 -1.9400 -1.6100 -1.6100 -1.6100 -1.6100 -1.6100 -1.6100 -1.6100 -1.6100 -1.6100 -1.6100 -1.6100 -1.6100 -1.6100 -1.6100 -1.6100 -1.6100 -1.6100 -1.6100 -1.6100 -1.6100 -1.6100 -1.6100 -1.6100 -1.6100 -1.2800 -1.2800 -1.2800 -1.2800 -1.2800 -1.2800 -1.2800 -1.2800 -1.2800 -1.2800 -1.2800 -1.2800 -1.2800 -1.2800 -1.2800 -1.2800 -1.2800 -1.2800 -1.2800 -1.2800 -1.2800 -1.2800 -1.2800 -1.2800 -0.9500 -0.9500 -0.9500 -0.9500 -0.9500 -0.9500 -0.9500 -0.9500 -0.9500 -0.9500 -0.9500 -0.9500 -0.9500 -0.9500 -0.9500 -0.9500 -0.9500 -0.9500 -0.9500 -0.9500 -0.9500 -0.9500 -0.9500 -0.9500 -0.6200 -0.6200 -0.6200 -0.6200 -0.6200 -0.6200 -0.6200 -0.6200 -0.6200 -0.6200 -0.6200 -0.6200 -0.6200 -0.6200 -0.6200 -0.6200 -0.6200 -0.6200 -0.6200 -0.6200 -0.6200 -0.6200 -0.6200 -0.6200 -0.2900 -0.2900 -0.2900 -0.2900 -0.2900 -0.2900 -0.2900 -0.2900 -0.2900 -0.2900 -0.2900 -0.2900 -0.2900 -0.2900 -0.2900 -0.2900 -0.2900 -0.2900 -0.2900 -0.2900 -0.2900 -0.2900 -0.2900 -0.2900 0.0400 0.0400 0.0400 0.0400 0.0400 0.0400 0.0400 0.0400 0.0400 0.0400 0.0400 0.0400 0.0400 0.0400 0.0400 0.0400 0.0400 0.0400 0.0400 0.0400 0.0400 0.0400 0.0400 0.0400 0.3700 0.3700 0.3700 0.3700 0.3700 0.3700 0.3700 0.3700 0.3700 0.3700 0.3700 0.3700 0.3700 0.3700 0.3700 0.3700 0.3700 0.3700 0.3700 0.3700 0.3700 0.3700 0.3700 0.3700
nullX2= g - d.*x1
nullX2 = 24×24
3.9000 3.4800 3.0600 2.6400 2.2200 1.8000 1.3800 0.9600 0.5400 0.1200 -0.3000 -0.7200 -1.1400 -1.5600 -1.9800 -2.4000 -2.8200 -3.2400 -3.6600 -4.0800 -4.5000 -4.9200 -5.3400 -5.7600 3.9000 3.4800 3.0600 2.6400 2.2200 1.8000 1.3800 0.9600 0.5400 0.1200 -0.3000 -0.7200 -1.1400 -1.5600 -1.9800 -2.4000 -2.8200 -3.2400 -3.6600 -4.0800 -4.5000 -4.9200 -5.3400 -5.7600 3.9000 3.4800 3.0600 2.6400 2.2200 1.8000 1.3800 0.9600 0.5400 0.1200 -0.3000 -0.7200 -1.1400 -1.5600 -1.9800 -2.4000 -2.8200 -3.2400 -3.6600 -4.0800 -4.5000 -4.9200 -5.3400 -5.7600 3.9000 3.4800 3.0600 2.6400 2.2200 1.8000 1.3800 0.9600 0.5400 0.1200 -0.3000 -0.7200 -1.1400 -1.5600 -1.9800 -2.4000 -2.8200 -3.2400 -3.6600 -4.0800 -4.5000 -4.9200 -5.3400 -5.7600 3.9000 3.4800 3.0600 2.6400 2.2200 1.8000 1.3800 0.9600 0.5400 0.1200 -0.3000 -0.7200 -1.1400 -1.5600 -1.9800 -2.4000 -2.8200 -3.2400 -3.6600 -4.0800 -4.5000 -4.9200 -5.3400 -5.7600 3.9000 3.4800 3.0600 2.6400 2.2200 1.8000 1.3800 0.9600 0.5400 0.1200 -0.3000 -0.7200 -1.1400 -1.5600 -1.9800 -2.4000 -2.8200 -3.2400 -3.6600 -4.0800 -4.5000 -4.9200 -5.3400 -5.7600 3.9000 3.4800 3.0600 2.6400 2.2200 1.8000 1.3800 0.9600 0.5400 0.1200 -0.3000 -0.7200 -1.1400 -1.5600 -1.9800 -2.4000 -2.8200 -3.2400 -3.6600 -4.0800 -4.5000 -4.9200 -5.3400 -5.7600 3.9000 3.4800 3.0600 2.6400 2.2200 1.8000 1.3800 0.9600 0.5400 0.1200 -0.3000 -0.7200 -1.1400 -1.5600 -1.9800 -2.4000 -2.8200 -3.2400 -3.6600 -4.0800 -4.5000 -4.9200 -5.3400 -5.7600 3.9000 3.4800 3.0600 2.6400 2.2200 1.8000 1.3800 0.9600 0.5400 0.1200 -0.3000 -0.7200 -1.1400 -1.5600 -1.9800 -2.4000 -2.8200 -3.2400 -3.6600 -4.0800 -4.5000 -4.9200 -5.3400 -5.7600 3.9000 3.4800 3.0600 2.6400 2.2200 1.8000 1.3800 0.9600 0.5400 0.1200 -0.3000 -0.7200 -1.1400 -1.5600 -1.9800 -2.4000 -2.8200 -3.2400 -3.6600 -4.0800 -4.5000 -4.9200 -5.3400 -5.7600
quiver(x1, x2, dx1,dx2,'AutoScaleFactor',0.5)
axis([x1min x1max x2min x2max])
xlabel('$x1$','Interpreter','latex')
ylabel('$x2$','Interpreter','latex')
title('Vector field example','Interpreter','latex')
% x=0:0.5:30;
x = linspace(0, 30, size(nullX1,1)); % Use 'linspace' To Create Correct Length 'x'
plot(x,nullX1,'r-')
hold on
plot(x,nullX2,'k-')
hold on
Experiment to get different results.
.

更多回答（0 个）

类别

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

标签

产品

Community Treasure Hunt

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

Start Hunting!

Translated by