plotting maximal lyapunov exponent using ode45

Question

Rizwana Junaid 2012-1-9

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/25637-plotting-maximal-lyapunov-exponent-using-ode45

 i m in need to plot the lyapunov exponent 'f vs lyapunov,' but i am     unable to run the program due to some error in the program. can anyone  pls help me to get the plot and any suggestions to make it perfect.

with kind regards

matlab codes:

 clc
 global f
 for f=0.0:0.1:30
 f
 initialx(1)=0.0100;initialx(2)=0.01;
 lyap(1)=.01;
 [t,x]=ode45('loreeneq',0:1:500,[initialx(1),initialx(2)]);
 lyap1=lyap([t,x(:,1)]);
 plot(f,lyap1,'r');
 hold on
 drawnow
 end
 xlabel ('f');ylabel('lyap')
--------------------------------------------------------------------------
 function dxdt=loreeneq(t,x) 
 global r
 dxdt1=10*(x(2)-x(1));
 dxdt2=(r*x(1))-x(2)-(x(1)*x(3));
 dxdt3=(x(1)*x(2))-(2.67*x(3));
 dxdt=[dxdt1;dxdt2;dxdt3];

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Walter Roberson 2012-1-9

It is faster for us if you show us the error message and the line it is complaining about.

Rizwana Junaid 2012-1-10

sorry i had pasted wrong main file. my code is

matlab codes:

clc

global r

for r=0.0:0.1:30

r

lyap(1)=.01;

[t,x]=ode45('loreeneq',0:1:500,[.01,.01,.01]);

lyap1=lyap([t,x(:,1)]);

plot(r,lyap1,'r');

drawnow

end

xlabel ('r');ylabel('lyap')

----------------------------------------------------------------------

function dxdt=loreeneq(t,x)

global r

dxdt1=10*(x(2)-x(1));

dxdt2=(r*x(1))-x(2)-(x(1)*x(3));

dxdt3=(x(1)*x(2))-(2.67*x(3));

dxdt=[dxdt1;dxdt2;dxdt3];

---------------------------------------------------------

error is:

f =

0

??? Subscript indices must either be real positive integers or logicals.

Error in ==> mlcmainbifr at 10

lyap1=lyap([t,x(:,1)]);

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Answer 1

Walter Roberson 2012-1-9

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/25637-plotting-maximal-lyapunov-exponent-using-ode45#answer_33610

In the top portion you have "global f", but you do not use "f" in the other portion. In the bottom portion you have "global r" but you do not use "r" in the other portion.

"global" shares by variable name. There is not just one global variable available. If you want to use the value of f in the bottom routine and you want to pass it via a global then you need to use "global f" in the bottom routine and reference f there instead of r.

If that is what you are trying to do then there are better approaches, which the ode45 documentation links to when it says to see the documentation on "parameterizing functions"