How to plot for a matrix?

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Westin Messer
Westin Messer 2018-11-6
回答： Stephen23 2018-11-6
Hello, in this code I am varying the parameter k from 1 to 4 and I get four different sets of numbers for u and v. I want to plot all sets of these numbers on the same graph so I should get multiple lines. However, when I run it, it only plots for one set of values. Does anyone know how to fix this? Thanks!
%Clear command window and workspace
clear
close all
clc
% Fitzhugh-Nagoma model parameters
e=0.01; k=1:1:4; a=0.1;
i = 0.001;
figure(1);
hold on
u=zeros(500000,4);
v=zeros(500000,4);
t=zeros(100000,1);
% Initial conditions:
u(:)=0.3;
v(:)=0.0;
t(1)=0;
dt=0.001;
%==========================================================================
% Forvard Euler Method, for soluing the ODE
%==========================================================================
for k=1:4
for i=1:1:500000
t(i+1)=t(i)+dt;
% u(i+1) = u(i)+ dt*((1/e)*((k(:)*u(i)*(u(i)-a)*(1-u(i)))-v(i)));
u(i+1,:) = u(i,:)+ dt.*((1/e).*((k.*(u(i,:).*(u(i,:)-a).*(1-u(i,:))))-v(i)));
v(i+1,:) = v(i,:)+ dt*(u(i)-v(i));
end
end
% Getting the phase plot
figure(1);
upts=(-2:.05:2);
unullpts=(k*upts.*(upts-a).*(1-upts));
vnullpts=upts;
plot(upts,unullpts,'black',upts,vnullpts,'black');
xlabel('u'); ylabel('v');
axis([-1 2 -1.5 5]);
plot(u,v,'b')
title('Nullcline Plot')
xlabel('u')
ylabel('v')

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采纳的回答

Stephen23
Stephen23 2018-11-6
You for to use the index k from the outer loop:
% Fitzhugh-Nagoma model parameters
e = 0.01;
k = 1:1:4;
a = 0.1;
i = 0.001;
u=zeros(5000,4);
v=zeros(5000,4);
t=zeros(1000,1);
% Initial conditions:
u(:)=0.3;
v(:)=0.0;
t(1)=0;
dt=0.001;
%
for k=1:4
for i=1:1:5000
t(i+1)=t(i)+dt;
u(i+1,k) = u(i,k)+ dt.*((1/e).*((k.*(u(i,k).*(u(i,k)-a).*(1-u(i,k))))-v(i)));
v(i+1,k) = v(i,k)+ dt*(u(i,k)-v(i,k));
end % ^ ^ ^ ^ you forgot to use |k|.
end
plot(t,u,'r', t,v,'b')
Gives:

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