[R] Log plus one transformation in R

[John Sorkin]

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 at 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 <faradj.g at 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 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.

    [[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.
Confidentiality Statement:
This email message, including any attachments, is for the sole use of
the intended recipient(s) and may contain confidential and privileged
information. Any unauthorized use, disclosure or distribution is
prohibited. If you are not the intended recipient, please contact the
sender by reply email and destroy all copies of the original message.