Dear Friends I am facing the problem of log values in R. The log(1-0.99999999999999999) is giving -Inf while log(1e-18) gives finite answer. Any suggestion to deal with this problem? Thank you
log of small values in R
4 messages · Shaami, Jeff Newmiller, David Winsemius +1 more
?log1p
On January 10, 2021 12:53:14 AM PST, Shaami <nzshaam at gmail.com> wrote:
Dear Friends I am facing the problem of log values in R. The log(1-0.99999999999999999) is giving -Inf while log(1e-18) gives finite answer. Any suggestion to deal with this problem? Thank you [[alternative HTML version deleted]]
______________________________________________ R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
Sent from my phone. Please excuse my brevity.
On Jan 10, 2021, at 11:38 PM, Jeff Newmiller <jdnewmil at dcn.davis.ca.us> wrote: ?log1p On January 10, 2021 12:53:14 AM PST, Shaami <nzshaam at gmail.com> wrote:
Dear Friends I am facing the problem of log values in R. The log(1-0.99999999999999999) is giving -Inf while log(1e-18) gives finite answer. Any suggestion to deal with this problem? Thank you
Jeff answers the specific question (of how to deal with the issue) but as to why?
0.9999999999999999999 == 1
[1] TRUE And you should switch your mail client to plain text in future contributions to Rhelp.
David. >> >> [[alternative HTML version deleted]] >> >> ______________________________________________ >> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see >> https://stat.ethz.ch/mailman/listinfo/r-help >> PLEASE do read the posting guide >> http://www.R-project.org/posting-guide.html >> and provide commented, minimal, self-contained, reproducible code. > > -- > Sent from my phone. Please excuse my brevity. > > ______________________________________________ > R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code.
2 days later
On Mon, 11 Jan 2021 at 08:22, Shaami <nzshaam at gmail.com> wrote:
Dear Friends I am facing the problem of log values in R. The log(1-0.99999999999999999) is giving -Inf while log(1e-18) gives finite answer. Any suggestion to deal with this problem? Thank you
This vignette has a lot of good information about log of small numbers. vignette(package = "Rmpfr", "log1mexp-note") https://cran.r-project.org/web/packages/Rmpfr/vignettes/log1mexp-note.pdf Regards Martin M. S. Pedersen