[R] Log plus one transformation in R

[David Winsemius]

> On Dec 12, 2016, at 8:53 AM, John Sorkin <jsorkin at 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

Read the help page more carefully.

-- 
David.
> 
> 
> 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)
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>>>> 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
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> 
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