How do I exclude the first ten observations in the line plot generated by the three differential equations

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Christopher 2025-6-4

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https://ww2.mathworks.cn/matlabcentral/answers/2177527-how-do-i-exclude-the-first-ten-observations-in-the-line-plot-generated-by-the-three-differential-equ

评论： Torsten 2025-6-5

在 MATLAB Online 中打开

close all

clear all

clc

tspan = [0 100];

y0 = 0.7; % initial value of state variable x1

r0 = 0.7; % initial value of state variable x2

w0 = 0.8; % initial value of state variable x3

x0 = [y0; r0; w0];

[t, x] = ode45(@odefcn, tspan, x0);

%% Plot x2 (y-axis) vs. x1 (x-axis)

subplot(3,1,1);

plot(t,x(:,1));

xlabel('Time')

ylabel('Output');

subplot(3,1,2);

plot(t,x(:,2));

xlabel('Time')

ylabel('Policy Rate');

subplot(3,1,3);

plot(t,x(:,3));

xlabel('Time')

ylabel('Wage Share');

y0 = [0.7; 0.7; 0.8];

%% System of three differential equations

function dx = odefcn(t, x)

% definitions

y = x(1);

r = x(2);

w = x(3);

% parameters

alpha = 1.0;

beta = 1.0;

gamma = 0.1;

delta = 0.3;

mu = 1.0;

lambda = 0.3;

theta = 0.1;

omega = 0.2;

% ODEs

dx(1,1) = alpha * y - beta * r * y;

dx(2,1) = - omega * r + gamma * w * r + delta * y * r;

dx(3,1) = - theta * w + lambda * y * w - mu * w * w;

end

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Christopher 2025-6-5

I was thinking in terms of timespan...

Torsten 2025-6-5

在 MATLAB Online 中打开

It's still not clear what you mean.

If you define

tspan = [0 100];

ode45 will choose the output times between 0 and 100 on its own. Thus excluding the first ten outputs does not tell you anything about the time points when these ten outputs were reported: they could be [0 1 2 3 4 5 6 7 8 9] or any other increasing vector with 10 elements starting at 0.

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回答（1 个）

Matt J 2025-6-4

编辑：Matt J 2025-6-4

在 MATLAB Online 中打开

One way,

tspan   = [0 100];
y0      =  0.7;   % initial value of state variable x1
r0      =  0.7;   % initial value of state variable x2
w0      =  0.8;   % initial value of state variable x3
x0      = [y0; r0; w0];
[t, x]  = ode45(@odefcn, tspan, x0);
x(1:10,:)=nan;