1
$\begingroup$

Consider the following paper:

https://reader.elsevier.com/reader/sd/pii/S0096300306007715?token=2B98E3B12F1E623C99A0787996469AF36E8EF230F6ED5289EAFB60B64CE79A6ACCF74B946A34F3370C65D4FC99018648&originRegion=eu-west-1&originCreation=20210825115609

From my understanding figure 2(on page 5) is a graph of $s(t), i(t)$ and $r(t)$ by the function in the appendix(page 6) for case 1.

However, when I try plotting this function, I get the wrong out output, why?

Plot[{ 1 - 
   0.36*t + (0.72*10^-1)*t^2 - (0.96*10^-2)*t^3 + (0.96*10^-3)*
    t^4 - (0.768*10^-4)*t^5 + (0.5688888892*10^-6)*t^6, 
  0.36*t - (0.72*10^-1)*t^2 + (0.96*10^-2)*t^3 - (0.96*10^-3)*
    t^4 + (0.768*10^-4)*t^5 - (0.512*10^-5)*t^6}, {t, 0, 10}]

enter image description here

$\endgroup$
7
  • 1
    $\begingroup$ The solutions in the Appendix are only approximate solutions, not exact; and power-series approximations get worse as their arguments get larger. Note that your graph is pretty good for smaller values of $t$ and only diverges at larger values. $\endgroup$ Sep 2 at 15:40
  • 7
    $\begingroup$ I’m voting to close this question because it arises from confusion about the applicability of certain published results, and has nothing to do with using the Mathematica software correctly or incorrectly. $\endgroup$ Sep 2 at 15:41
  • $\begingroup$ @MichaelSeifert I meant, my plot isn't plotting what the paper plotted.. $\endgroup$
    – Math
    Sep 6 at 11:57
  • $\begingroup$ Presumably the paper is plotting that actual numerical solutions to the differential equations. The Appendix gives power-series approximations to these solutions, not the actual functions (which I suspect can't be written in closed form.) $\endgroup$ Sep 6 at 13:50
  • $\begingroup$ @MichaelSeifert isn't that defeating the purpose of Adomian decomposition? surely they should be plotting their solutions from Adomian decomposition rather than "actual" numerical solutions? that's what I would've thought anyway.. I have the actual numerical solutions and they match their plots but this is strange since that's not our objective! $\endgroup$
    – Math
    Sep 6 at 14:01