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invalid index in program
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p=8/3;
r=25;
sigma=10;
npoints =5000;
dt = 0.1;
a = zeros(npoints,1);
b = zeros(npoints,1);
c= zeros(npoints,1);
t = zeros(npoints,1);
//t=1:dt:100;
Invalid use of operator.
a(1)=1;
b(1)=1;
c(1)=1;
suma=0;
sumb=0;
sumc=0;
sumS=0;
sumZ=0;
for i = 1:npoints-1
sumS=sumS+a(i)*c(i-npoints);
sumZ=sumZ+a(i)*b(i-npoints);
a(i+1)=((sigma)/(i+1))*(b(i)-a(i));
b(i+1)=(1/(i+1))*(r*a(i)-b(i)-sumS);
c(i+1)=(1/(i+1))*(sumZ-p*c(i));
suma=suma+a(i).*(t^i);
sumb=sumb+b(i).*(t^i);
sumc=sumc+c(i).*(t^i);
t(i+1) = t(i) + dt;
end;
plot(t,suma)
pl revise the program
20 Comments
Jan
on 24 Feb 2022
@shiv gaur: Again: Please explain as accurate as possible what the problem with your code is. You see, that the "//" is not accepted by Matlab, so simply remove it.
The explanation, that the code should show the Lorenz attractor does not help to understand, what your problem is.
shiv gaur
on 24 Feb 2022
Edited: Jan
on 24 Feb 2022
p=8/3;
r=25;
sigma=10;
npoints =5000;
dt = 0.1;
a = zeros(npoints,1);
b = zeros(npoints,1);
c= zeros(npoints,1);
t = zeros(npoints,1);
a(1)=1;
b(1)=1;
c(1)=1;
suma=0;
sumb=0;
sumc=0;
sumS=0;
sumZ=0;
for i = 1:npoints-1
sumS=sumS+a(i)*c(i-npoints);
sumZ=sumZ+a(i)*b(i-npoints);
a(i+1)=((sigma)/(i+1))*(b(i)-a(i));
b(i+1)=(1/(i+1))*(r*a(i)-b(i)-sumS);
c(i+1)=(1/(i+1))*(sumZ-p*c(i));
suma=suma+a(i).*(t^i);
sumb=sumb+b(i).*(t^i);
sumc=sumc+c(i).*(t^i);
t(i+1) = t(i) + dt;
end;
plot(t,suma)
revise program
shiv gaur
on 24 Feb 2022
this is the lorenz attractor problem that can be solve by power series method i make code by power series method iplace of ode system the result of lorenz by ode is not matching by power series my program of power series lorenz
shiv gaur
on 24 Feb 2022
Edited: Rik
on 24 Feb 2022
this is the program of lorenz using time step
p=8/3;
r=25;
sigma=10;
npoints =500000;
dt = 0.0001;
a = zeros(npoints,1);
b = zeros(npoints,1);
c = zeros(npoints,1);
time = zeros(npoints,1);
a(1)=1;
b(1)=1;
c(1)=1;
for step = 1:npoints-1
a(step+1)=a(step)+sigma*(b(step)-a(step))*dt;
b(step+1)=b(step)+(-x(step)*c(step)+r*a(step)-b(step))*dt;
c(step+1)=c(step)+(a(step)*b(step)-p*z(step))*dt;
time(step+1) = time(step) + dt;
end;
Unrecognized function or variable 'x'.
subplot (2,1,1);
plot(time,z,'b' );
xlabel('time');
ylabel('z');
subplot (2,1,2);
plot (x,z,'g' );
xlabel('x');
ylabel('z')
2.power series
p=8/3;
r=25;
sigma=10;
npoints =5000;
dt = 0.1;
a = zeros(npoints,1);
b = zeros(npoints,1);
c= zeros(npoints,1);
t = zeros(npoints,1);
a(1)=1;
b(1)=1;
c(1)=1;
suma=0;
sumb=0;
sumc=0;
sumS=0;
sumZ=0;
for i = 1:npoints-1
sumS=sumS+a(i)*c(i-npoints);
sumZ=sumZ+a(i)*b(i-npoints);
a(i+1)=((sigma)/(i+1))*(b(i)-a(i));
b(i+1)=(1/(i+1))*(r*a(i)-b(i)-sumS);
c(i+1)=(1/(i+1))*(sumZ-p*c(i));
suma=suma+a(i).*(t^i);
sumb=sumb+b(i).*(t^i);
sumc=sumc+c(i).*(t^i);
t(i+1) = t(i) + dt;
end;
plot(t,sumb)
why not giving match plot
Rik
on 24 Feb 2022
I understand that there may be a language barrier, but I can't imagine that in your native language 'revise program' would be considered a polite request. You're asking strangers to do you a favor. Right now it looks like you're not prepared to put in any effort explaining your question. Lucky for you that Walter and Jan are kinder than I am.
Please read the link that Jan provided. Please use interpunction and line breaks. Remember that it is easy for people to ignore your post. If you make your problem clear, you will increase the chances that someone will enjoy your question as a puzzle. The puzzle should not be understanding your question, but rather how to solve it.
You have accepted 3 answers out of the many your received. You should consider how you can make your questions different so you actually get answers that solve enough of your questions to be accepted.
Jan
on 24 Feb 2022
@shiv gaur: The code you have posted does not run:
b(step+1)=b(step)+(-x(step)*c(step)+r*a(step)-b(step))*dt;
% ^ x is undefined
There is no chance to guess, what your problem is. You do not mention, what your problem is. Your code does not run and in consequence it does not show, what your problem is.
So how can we help you?
- Post running code.
- Use left button of the toolbar's "Code" section to format the code to improve the readbility.
- Explain in clear word, what the problem is.
shiv gaur
on 24 Feb 2022
Edited: Rik
on 24 Feb 2022
p=8/3;
r=25;
sigma=10;
npoints =500000;
dt = 0.0001;
a = zeros(npoints,1);
b = zeros(npoints,1);
c = zeros(npoints,1);
time = zeros(npoints,1);
a(1)=1;
b(1)=1;
c(1)=1;
for step = 1:npoints-1
a(step+1)=a(step)+sigma*(b(step)-a(step))*dt;
b(step+1)=b(step)+(-a(step)*c(step)+r*a(step)-b(step))*dt;
c(step+1)=c(step)+(a(step)*b(step)-p*z(step))*dt;
time(step+1) = time(step) + dt;
end;
Unrecognized function or variable 'z'.
subplot (2,1,1);
plot(time,z,'b' );
xlabel('time');
ylabel('z');
subplot (2,1,2);
plot (x,z,'g' );
xlabel('x');
ylabel('z')
this is edit program lorenz
2.program using power series not matching
2.power series
p=8/3;
r=25;
sigma=10;
npoints =5000;
dt = 0.1;
a = zeros(npoints,1);
b = zeros(npoints,1);
c= zeros(npoints,1);
t = zeros(npoints,1);
a(1)=1;
b(1)=1;
c(1)=1;
suma=0;
sumb=0;
sumc=0;
sumS=0;
sumZ=0;
for i = 1:npoints-1
sumS=sumS+a(i)*c(i-npoints);
sumZ=sumZ+a(i)*b(i-npoints);
a(i+1)=((sigma)/(i+1))*(b(i)-a(i));
b(i+1)=(1/(i+1))*(r*a(i)-b(i)-sumS);
c(i+1)=(1/(i+1))*(sumZ-p*c(i));
suma=suma+a(i).*(t^i);
sumb=sumb+b(i).*(t^i);
sumc=sumc+c(i).*(t^i);
t(i+1) = t(i) + dt;
end;
plot(t,sumb)
why not giving match plot
Jan
on 24 Feb 2022
Edited: Jan
on 24 Feb 2022
@shiv gaur: Seriously?! Both code block are still not running:
c(step+1)=c(step)+(a(step)*b(step)-p*z(step))*dt;
% ^ undefined variable z
and:
sumS=sumS+a(i)*c(i-npoints);
% ^^^^^^^^^ causes a negative index
Your question "why not giving match plot" is not meaningful: Both codes do not procude any plot, because they stop with errors.
You do not care about a proper formating - do you see, that I've spend the time for apply the code formatting in your contributions? You repeatedly post not running code. You ignore questions for clarifications still do not mention, what the problem is you want to solve.
This is not a fair usage of this forum.
Please confirm, that you have read and understood this: https://www.mathworks.com/matlabcentral/answers/6200-tutorial-how-to-ask-a-question-on-answers-and-get-a-fast-answer
shiv gaur
on 24 Feb 2022
sorry jan this is edit program that is running program this is the program of lorenz using time step
we have to plan match with below program using power series now program is right
p=8/3;
r=25;
sigma=10;
npoints =500000;
dt = 0.0001;
a = zeros(npoints,1);
b = zeros(npoints,1);
c = zeros(npoints,1);
time = zeros(npoints,1);
a(1)=1;
b(1)=1;
c(1)=1;
for step = 1:npoints-1
a(step+1)=a(step)+sigma*(b(step)-a(step))*dt;
b(step+1)=b(step)+(-a(step)*c(step)+r*a(step)-b(step))*dt;
c(step+1)=c(step)+(a(step)*b(step)-p*c(step))*dt;
time(step+1) = time(step) + dt;
end;
subplot (2,1,1);
plot(time,z,'b' );
xlabel('time');
ylabel('z');
subplot (2,1,2);
plot (x,z,'g' );
xlabel('x');
ylabel('z')
2.power series
p=8/3;
r=25;
sigma=10;
npoints =5000;
dt = 0.1;
a = zeros(npoints,1);
b = zeros(npoints,1);
c= zeros(npoints,1);
t = zeros(npoints,1);
a(1)=1;
b(1)=1;
c(1)=1;
suma=0;
sumb=0;
sumc=0;
sumS=0;
sumZ=0;
for i = 1:npoints-1
sumS=sumS+a(i)*c(i-npoints);
sumZ=sumZ+a(i)*b(i-npoints);
a(i+1)=((sigma)/(i+1))*(b(i)-a(i));
b(i+1)=(1/(i+1))*(r*a(i)-b(i)-sumS);
c(i+1)=(1/(i+1))*(sumZ-p*c(i));
suma=suma+a(i).*(t^i);
sumb=sumb+b(i).*(t^i);
sumc=sumc+c(i).*(t^i);
t(i+1) = t(i) + dt;
end;
plot(t,sumb)
why not giving match plot
Answers (2)
Walter Roberson
on 24 Feb 2022
npoints =5000;
for i = 1:npoints-1
sumS=sumS+a(i)*c(i-npoints);
First iteration: i is 1, and a(1) is being indexed; as you initialized a(1) that is valid so far.
Then c(i-npoints) is being indexed. That is c(1-5000) which is c(-4999) which is not a valid index.
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