Timeline for Specifying history for delay differential equations ``near infinity'' (using NDSolve)
Current License: CC BY-SA 4.0
12 events
| when toggle format | what | by | license | comment | |
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| Feb 3, 2019 at 23:23 | comment | added | Michael E2 | You haven't accepted any answers to any of your questions. You can accept the answer, if any, that solves your problem, by clicking the checkmark sign. | |
| Feb 1, 2019 at 19:03 | history | bumped | CommunityBot | This question has answers that may be good or bad; the system has marked it active so that they can be reviewed. | |
| Jan 5, 2019 at 19:13 | comment | added | Somos | I am curious. How did you get from your DDE to $\,f''(x)+f(x) \approx 0\,$ since you want $\,f(x) \approx \sin x\,$ for large $x$? If you meant $\,f(x+2\pi)\,$ instead of $\,f(x+1)\,$ that would make sense. | |
| Jan 2, 2019 at 12:46 | comment | added | Sina | That is what I meant by ``history''; in fact that is the only way NDSolve can integrate a DDE. Still if you set up the history at t>=0 and integrate from zero, you will get a different answer from a history at t>=1 which is integrated from t=1. And that is my problem, because how close to infinity is close enough? how do I know I can trust the result. | |
| Jan 2, 2019 at 9:52 | answer | added | Ulrich Neumann | timeline score: 3 | |
| Jan 2, 2019 at 9:47 | answer | added | Cesareo | timeline score: 2 | |
| Jan 2, 2019 at 9:34 | comment | added | Ulrich Neumann |
In the documentation of NDSolveValue I found an example which might help(NDSolveValue[{x'[t] == x[t] (x[t - Pi] - x'[t - 1]), x[t /; t <= 0] == Cos[t]}, x, {t, 0, 8}]): Instead of initial conditions try f[t /; t >= 0] == Sin[t]
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| Jan 2, 2019 at 2:34 | comment | added | Somos |
Ah, yes. I should have mentioned that I don't think NDSolve[] is going to help.
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| Jan 2, 2019 at 2:25 | history | edited | Sina | CC BY-SA 4.0 |
added 31 characters in body; edited title
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| Jan 2, 2019 at 2:22 | comment | added | Sina | Thanks Somos, but my question is how to use NDSolve to handle this problem. | |
| Jan 2, 2019 at 2:06 | comment | added | Somos | Plase read Math Stackexchange question 2765086 "Writing the recursive as explicit" and its answers for ideas. Also see [MSE question 2245492] (math.stackexchange.com/q/2245492) "Continuous recursive iteration" for $\,f'(x)=f(x-1).$ | |
| Jan 2, 2019 at 0:23 | history | asked | Sina | CC BY-SA 4.0 |