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wlyra / covid19

SIR code in python to model the spread of COVID-19
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What is alpha_ts, beta_ts, Cdt? #3

Open Richarizardd opened 4 years ago

Richarizardd commented 4 years ago

In your RK3 function, was wondering how you calculated: alpha_ts, beta_ts, and Cdt

jcert commented 4 years ago

It is some implementation of a third-order Runge-Kutta method. But I can't really figure which third method it is and how those coefficients were calculated.

wlyra commented 4 years ago

Yes, these are the coefficients for a low storage 3rd order Runge-Kutta, from Williamson et al. 1980

https://www.sciencedirect.com/science/article/pii/0021999180900339?via%3Dihub

Also explained here

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19940029698.pdf

and here (appendix H4)

http://pencil-code.nordita.org/doc/manual.pdf

On Fri, Mar 27, 2020 at 10:03 AM jair notifications@github.com wrote:

It is some implementation of a third-order Runge-Kutta method https://en.wikipedia.org/wiki/List_of_Runge%E2%80%93Kutta_methods#Kutta's_third-order_method. But I can't really figure which third method it is and how those coefficients were calculated.

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