MATLAB Answers

Ode45, evolution giving NaNs after some time, with no evidence of singularities in the equations

3 views (last 30 days)
Attached is a simple integrator for four coupled first order ode s.
after a certain time, the 4-vector solution turns into NaNs with no evidence of singularities in the equations.
This happens after a certain range where the solutions (starting as real) are written in complex notation although the imaginary part is zero. (why?)
can anyone please have a look and let me know if there's something im missing?
Mohammad Farhat
Mohammad Farhat on 7 Apr 2020
yes I said the notation at somepoint (if you check the entries of the solutions), for no apparent reason to me at least, becomes a complex notation, although as you've seen the solution is still purely real.

Sign in to comment.

Accepted Answer

Walter Roberson
Walter Roberson on 7 Apr 2020
Your first order, e1, gets to be more than 1.0, and then the sqrt(1-x^2) gets to be complex. Problems accumulate from there.
What are the original equations that you are trying to deal with? Do you have the Symbolic Toolbox ?
Walter Roberson
Walter Roberson on 8 Apr 2020
I do not think an event function is appropriate here. Projection and failed steps is normal for ode45() .
Setting a MaxStep in the options might potentially help.

Sign in to comment.

More Answers (0)





Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!