[R] Log plus one transformation in R

[Faradj Koliev]

Many thanks! 

logp1(x) worked just fine.

Best,
Faradj

Skickat från min iPhone

> 12 dec. 2016 kl. 22:54 skrev peter dalgaard <pdalgd at 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 at 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 <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
>>> 
>>> 
>>> 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
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>>>> posting-guide.html
>>>> and provide commented, minimal, self-contained, reproducible code.
>>> 
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>>> 
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>> 
>> ______________________________________________
>> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
>> https://stat.ethz.ch/mailman/listinfo/r-help
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>> 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.mes at cbs.dk  Priv: PDalgd at gmail.com
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