Many thanks! logp1(x) worked just fine.
Best, Faradj Skickat från min iPhone > 12 dec. 2016 kl. 22:54 skrev peter dalgaard <pda...@gmail.com>: > > And, for crying out loud... just try it with x = 1.234e-16 or so. One would > think that the hint |x| << 1 was obvious enough. > > -pd > >> On 12 Dec 2016, at 18:26 , William Dunlap via R-help <r-help@r-project.org> >> wrote: >> >> Print more digits of the quotient or subtract one from it and you will see >> the difference: >> >>> log1p(0.000001)/log(0.000001+1) - 1 >> [1] 8.22666379463044e-11 >> >> >> Bill Dunlap >> TIBCO Software >> wdunlap tibco.com >> >> On Mon, Dec 12, 2016 at 8:53 AM, John Sorkin <jsor...@grecc.umaryland.edu> >> wrote: >> >>> At the risk of being flamed . . . >>> What is the difference between log1p(x) and log(x+1)? >>> The two methods appear to give the same results: >>>> log1p(0.000001)/log(0.000001+1) >>> [1] 1 >>> John >>> >>> >>> John David Sorkin M.D., Ph.D. >>> Professor of Medicine >>> Chief, Biostatistics and Informatics >>> University of Maryland School of Medicine Division of Gerontology and >>> Geriatric Medicine >>> Baltimore VA Medical Center >>> 10 North Greene Street >>> GRECC (BT/18/GR) >>> Baltimore, MD 21201-1524 >>> (Phone) 410-605-7119 >>> (Fax) 410-605-7913 (Please call phone number above prior to faxing) >>> >>>>>> William Dunlap via R-help <r-help@r-project.org> 12/12/16 11:38 AM >>> >>> log1p(x), in the base package computes log(1+x) accurately for small x (and >>> large). >>> >>> E.g., >>>> options(digits=16) >>>> base::log1p(1e-14) >>> [1] 9.99999999999995e-15 >>>> base::log1p(1e-14) - base::log(1+1e-14) >>> [1] 7.992778373591124e-18 >>>> as.numeric(log(Rmpfr::mpfr(1,precBits=1000) + Rmpfr::mpfr(1e-14, >>> precBits=1000))) - log1p(1e-14) >>> [1] 0 >>> >>> >>> Bill Dunlap >>> TIBCO Software >>> wdunlap tibco.com >>> >>>> On Mon, Dec 12, 2016 at 8:23 AM, Faradj Koliev <farad...@gmail.com> wrote: >>>> >>>> Hi all, >>>> >>>> How do I perform log(x+1) in R? >>>> >>>> log1p_trans() from the package ”scales" doesn’t seem to work for me. >>>> >>>> Best, >>>> Faradj >>>> ______________________________________________ >>>> R-help@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. >>> >>> [[alternative HTML version deleted]] >>> >>> ______________________________________________ >>> R-help@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. >>> >>> *Confidentiality Statement:* >>> >>> This email message, including any attachments, is for ...{{dropped:10}} >> >> ______________________________________________ >> R-help@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. > > -- > Peter Dalgaard, Professor, > Center for Statistics, Copenhagen Business School > Solbjerg Plads 3, 2000 Frederiksberg, Denmark > Phone: (+45)38153501 > Office: A 4.23 > Email: pd....@cbs.dk Priv: pda...@gmail.com > > > > > > > > > ______________________________________________ R-help@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.
