# How can I use Lorenz Attractor code?

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Darwin Tuazon2019-5-25

Hi everyone!
i want to simulate Lorenz Attractor using the script I found in Matlab File Exchange by Moiseev Igor. But I do not know how to input my parametes here.
my parameters are
sigma= 10
beta=8/3;
rho=28
x=5
y=5
z=5
and i want to integrate it from t=0 to 20.
function [x,y,z] = lorenz(rho, sigma, beta, initV, T, eps)
% LORENZ Function generates the lorenz attractor of the prescribed values
% of parameters rho, sigma, beta
%
% [X,Y,Z] = LORENZ(RHO,SIGMA,BETA,INITV,T,EPS)
% X, Y, Z - output vectors of the strange attactor trajectories
% RHO - Rayleigh number
% SIGMA - Prandtl number
% BETA - parameter
% INITV - initial point
% T - time interval
% EPS - ode solver precision
%
% Example.
% [X Y Z] = lorenz(28, 10, 8/3);
% plot3(X,Y,Z);
if nargin<3
error('MATLAB:lorenz:NotEnoughInputs','Not enough input arguments.');
end
if nargin<4
eps = 0.000001;
T = [0 25];
initV = [0 1 1.05];
end
options = odeset('RelTol',eps,'AbsTol',[eps eps eps/10]);
[T,X] = ode45(@(T,X) F(T, X, sigma, rho, beta), T, initV, options);
plot3(X(:,1),X(:,2),X(:,3));
axis equal;
grid;
title('Lorenz attractor');
xlabel('X'); ylabel('Y'); zlabel('Z');
x = X(:,1);
y = X(:,2);
z = X(:,3);
return
end
function dx = F(T, X, sigma, rho, beta)
% Evaluates the right hand side of the Lorenz system
% x' = sigma*(y-x)
% y' = x*(rho - z) - y
% z' = x*y - beta*z
% typical values: rho = 28; sigma = 10; beta = 8/3;
dx = zeros(3,1);
dx(1) = sigma*(X(2) - X(1));
dx(2) = X(1)*(rho - X(3)) - X(2);
dx(3) = X(1)*X(2) - beta*X(3);
return
end
Thank you and have a nice day.
##### 2 个评论显示隐藏 1更早的评论
Darwin Tuazon 2019-5-25
I'm confused to function [x,y,z] = lorenz(rho, sigma, beta, initV, T, eps)
Parameters values are sigma= 10; beta=8/3; rho=28;
and my intial values is x=5; y=5; z=5

### 回答（3 个）

Hi,
You were not executing the codes properly. Here is a single code that associates both scripts into one. Now it is much simpler.
sigma=10; beta=8/3; ro=28; % Your data
ICs=[5, 5, 5]; % Your data
t=[0, 20];
OPTs = odeset('reltol', 1e-6, 'abstol', 1e-8);
[time, fOUT]=ode45(@(t, x)([-sigma*x(1)+sigma*x(2); -x(2)-x(1).*x(3); -beta*x(3)+x(1).*x(2)-beta*ro]), t, ICs, OPTs);
close all
figure
plot3(fOUT(:,1), fOUT(:,2), fOUT(:,3)), grid
xlabel('x(t)'), ylabel('y(t)'), zlabel('z(t)')
title('LORENZ functions x(t) vs. y(t) vs. z(t)')
axis tight
figure
comet3(fOUT(:,1), fOUT(:,2), fOUT(:,3))
figure
subplot(311)
plot(time, fOUT(:,1), 'b','linewidth', 3), grid minor
title 'LORENZ functions x(t), y(t), z(t)', xlabel 'time', ylabel 'x(t)'
subplot(312)
plot( time', fOUT(:,2), 'r', 'linewidth', 2 ), grid minor
xlabel 'time', ylabel 'y(t)'
subplot(313)
plot(time, fOUT(:,3),'k', 'linewidth', 2), grid minor, xlabel 'time', ylabel 'z(t)'
figure
plot(fOUT(:,1), fOUT(:,2), 'b', 'linewidth', 1.5)
grid minor, title('LORENZ functions'), xlabel('x(t)'), ylabel 'y(t)'
axis square
figure
plot(fOUT(:,1), fOUT(:,3), 'k', 'linewidth', 1.5)
grid minor, title('LORENZ functions'), xlabel('x(t)'), ylabel 'z(t)'
axis square
figure
plot(fOUT(:,2), fOUT(:,3), 'm', 'linewidth', 1.5)
grid minor, title('LORENZ functions'), xlabel('y(t)'), ylabel 'z(t)'
axis square
Good luck.
##### 3 个评论显示隐藏 2更早的评论
Ghofran Khaled 2021-11-15
I posted it before and didn't get an answer
The question is in this link

Hi Darwin,
Here is my version of the Lorenz Atractor simulation code:
function df = LORENZ_sys_1ODE(~, x)
% HELP: Lorenz Functions
% dx/dt=-sigma*x+sigma*y;
% dy/dt=- y-x*z;
% dz/dt=-beta*z+x*y-beta*ro;
sigma=10; beta=8/3; ro=28;
% ICs: x(0)=5; y(0)=5; z(0)=5; % Your ICs
df=[-sigma*x(1)+sigma*x(2); ...
-x(2)-x(1).*x(3);...
-beta*x(3)+x(1).*x(2)-beta*ro];
end
Run this part to simulate the whole system
ICs=[5, 5, 5]; % Your data
t=[0, 20]; % Your simulation space
OPTs = odeset('reltol', 1e-6, 'abstol', 1e-8); % Optional ODE options set up
[time, fOUT]=ode45(@LORENZ_sys_1ODE, t, ICs, OPTs);
close all
figure
plot3(fOUT(:,1), fOUT(:,2), fOUT(:,3)), grid
xlabel('x(t)'), ylabel('y(t)'), zlabel('z(t)')
title('LORENZ functions x(t) vs. y(t) vs. z(t)')
axis tight
figure
comet3(fOUT(:,1), fOUT(:,2), fOUT(:,3))
figure
subplot(311)
plot(time, fOUT(:,1), 'b','linewidth', 3), grid minor
title 'LORENZ functions x(t), y(t), z(t)', xlabel 'time', ylabel 'x(t)'
subplot(312)
plot( time', fOUT(:,2), 'r', 'linewidth', 2 ), grid minor
xlabel 'time', ylabel 'y(t)'
subplot(313)
plot(time, fOUT(:,3),'k', 'linewidth', 2), grid minor, xlabel 'time', ylabel 'z(t)'
figure
plot(fOUT(:,1), fOUT(:,2), 'b', 'linewidth', 1.5)
grid minor, title('LORENZ functions'), xlabel('x(t)'), ylabel 'y(t)'
axis square
figure
plot(fOUT(:,1), fOUT(:,3), 'k', 'linewidth', 1.5)
grid minor, title('LORENZ functions'), xlabel('x(t)'), ylabel 'z(t)'
axis square
figure
plot(fOUT(:,2), fOUT(:,3), 'm', 'linewidth', 1.5)
grid minor, title('LORENZ functions'), xlabel('y(t)'), ylabel 'z(t)'
axis square
Good luck.
##### 1 个评论显示隐藏 无
Darwin Tuazon 2019-5-26
Thank you for your response. I compile your code Sulaymon Eshkabilov but there is an error.
>> LORENZ_sys_1ODE
Error: File: LORENZ_sys_1ODE.m Line: 7 Column: 11
Incorrect use of '=' operator. To assign a value to a variable, use '='. To compare values for
equality, use '=='.
Is there anything I did wrong?
function df = LORENZ_sys_1ODE(~, x)
% % HELP: Lorenz Functions
% % dx/dt=-sigma*x+sigma*y;
% % dy/dt=- y-x*z;
% % dz/dt=-beta*z+x*y-beta*ro;
sigma=10; beta=8/3; ro=28;
ICs: x(0) =5; y(0) = 5; z(0) = 5; % Your ICs
df=[-sigma*x(1)+sigma*x(2); ...
-x(2)-x(1).*x(3);...
-beta*x(3)+x(1).*x(2)-beta*ro];
ICs=[5, 5, 5]; % Your data
t=[0, 20]; % Your simulation space
OPTs = odeset('reltol', 1e-6, 'abstol', 1e-8); % Optional ODE options set up
[time, fOUT]=ode45(@LORENZ_sys_1ODE, t, ICs, OPTs);
close all
figure
plot3(fOUT(:,1), fOUT(:,2), fOUT(:,3)), grid
xlabel('x(t)'), ylabel('y(t)'), zlabel('z(t)')
title('LORENZ functions x(t) vs. y(t) vs. z(t)')
axis tight
figure
comet3(fOUT(:,1), fOUT(:,2), fOUT(:,3))
figure
subplot(311)
plot(time, fOUT(:,1), 'b','linewidth', 3), grid minor
title 'LORENZ functions x(t), y(t), z(t)', xlabel 'time', ylabel 'x(t)'
subplot(312)
plot( time', fOUT(:,2), 'r', 'linewidth', 2 ), grid minor
xlabel 'time', ylabel 'y(t)'
subplot(313)
plot(time, fOUT(:,3),'k', 'linewidth', 2), grid minor, xlabel 'time', ylabel 'z(t)'
figure
plot(fOUT(:,1), fOUT(:,2), 'b', 'linewidth', 1.5)
grid minor, title('LORENZ functions'), xlabel('x(t)'), ylabel 'y(t)'
axis square
figure
plot(fOUT(:,1), fOUT(:,3), 'k', 'linewidth', 1.5)
grid minor, title('LORENZ functions'), xlabel('x(t)'), ylabel 'z(t)'
axis square
figure
plot(fOUT(:,2), fOUT(:,3), 'm', 'linewidth', 1.5)
grid minor, title('LORENZ functions'), xlabel('y(t)'), ylabel 'z(t)'
axis square
end

Sulaymon Eshkabilov 2021-11-14
You simulated the code incorrectly. Here is how you should run the code in one m-file:
ICs=[5, 5, 5]; % Your data
t=[0, 20]; % Your simulation space
OPTs = odeset('reltol', 1e-6, 'abstol', 1e-8); % Optional ODE options set up
[time, fOUT]=ode45(@LORENZ_sys_1ODE, t, ICs, OPTs);
close all
figure
plot3(fOUT(:,1), fOUT(:,2), fOUT(:,3)), grid
xlabel('x(t)'), ylabel('y(t)'), zlabel('z(t)')
title('LORENZ functions x(t) vs. y(t) vs. z(t)')
axis tight
figure
comet3(fOUT(:,1), fOUT(:,2), fOUT(:,3))
figure
subplot(311)
plot(time, fOUT(:,1), 'b','linewidth', 3), grid minor
title 'LORENZ functions x(t), y(t), z(t)', xlabel 'time', ylabel 'x(t)'
subplot(312)
plot( time', fOUT(:,2), 'r', 'linewidth', 2 ), grid minor
xlabel 'time', ylabel 'y(t)'
subplot(313)
plot(time, fOUT(:,3),'k', 'linewidth', 2), grid minor, xlabel 'time', ylabel 'z(t)'
figure
plot(fOUT(:,1), fOUT(:,2), 'b', 'linewidth', 1.5)
grid minor, title('LORENZ functions'), xlabel('x(t)'), ylabel 'y(t)'
axis square
figure
plot(fOUT(:,1), fOUT(:,3), 'k', 'linewidth', 1.5)
grid minor, title('LORENZ functions'), xlabel('x(t)'), ylabel 'z(t)'
axis square
figure
plot(fOUT(:,2), fOUT(:,3), 'm', 'linewidth', 1.5)
grid minor, title('LORENZ functions'), xlabel('y(t)'), ylabel 'z(t)'
axis square
function df = LORENZ_sys_1ODE(~, x)
% HELP: Lorenz Functions
% dx/dt=-sigma*x+sigma*y;
% dy/dt=- y-x*z;
% dz/dt=-beta*z+x*y-beta*ro;
sigma=10; beta=8/3; ro=28;
% ICs: x(0)=5; y(0)=5; z(0)=5; % Your ICs
df=[-sigma*x(1)+sigma*x(2); ...
-x(2)-x(1).*x(3);...
-beta*x(3)+x(1).*x(2)-beta*ro];
end

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