Re: polyroot behaviour
Deepayan Sarkar <[email protected]>
| Newsgroups | gmane.comp.lang.r.general |
|---|---|
| Message-ID | <CADfFDC66vKuPpq_JKHjCj093aVGdEjZ-3ZxDzewLtU96aH_==w@mail.gmail.com> |
How can an odd degree polynomial be positive for all x? Deepayan On Thu, 2 Oct, 2025, 6:14 pm tgs77m--- via R-help, <[email protected]> wrote: > Colleagues, > > g <- function(x) ( x^11 + 1000*x^10 + 500 *x^9 + 1 ) > coeffs <- c(1, rep(0, 8), 500, 1000, 1) > roots <- polyroot(coeffs) > > Output > > [1] 0.25770068+3.958197e-01i > [2] -0.34615184+3.782848e-01i > [3] -0.04089779-4.838134e-01i > [4] 0.44124314-1.517731e-01i > [5] -0.04089779+4.838134e-01i > [6] -0.56201931-1.282822e-01i > [7] -0.34615184-3.782848e-01i > [8] 0.44124314+1.517731e-01i > [9] -0.56201931+1.282822e-01i > [10] 0.25770068-3.958197e-01i > [11] -999.49974975+1.110223e-16i > > [11] -999.49974975+1.110223e-16i makes no sense since f>0 for all x > > Why does polyroot do this? > > Thomas Subia > > ______________________________________________ > [email protected] mailing list -- To UNSUBSCRIBE and more, see > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide > https://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. > [[alternative HTML version deleted]]