From m@rc_@chw@rtz @end|ng |rom me@com  Thu Jan  9 17:52:19 2020
From: m@rc_@chw@rtz @end|ng |rom me@com (Marc Schwartz)
Date: Thu, 9 Jan 2020 11:52:19 -0500
Subject: [Rd] mean
In-Reply-To: <692FB5BD-523B-4498-9F95-78B17866B5E3@gmail.com>
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Message-ID: <753F0139-3672-4D36-BC59-DA0877C054FE@me.com>

Peter,

Thanks for the reply.

If that were the case, then should not the following be allowed to work with ordered factors?

> median(factor(c("1", "2", "3"), ordered = TRUE))
Error in median.default(factor(c("1", "2", "3"), ordered = TRUE)) : 
  need numeric data

At least on the surface, if you can lexically order a character vector:

> median(c("red", "blue", "green"))
[1] "green"

you can also order a factor, or ordered factor, and if the number of elements is odd, return a median value.

Regards,

Marc


> On Jan 9, 2020, at 10:46 AM, peter dalgaard <pdalgd at gmail.com> wrote:
> 
> I think median() behaves as designed: As long as the argument can be ordered, the "middle observation" makes sense, except when the middle falls between two categories, and you can't define and average of the two candidates for a median.
> 
> The "sick man" would seem to be var(). Notice that it is also inconsistent with cov():
> 
>> cov(c("1","2","3","4"),c("1","2","3","4") )
> Error in cov(c("1", "2", "3", "4"), c("1", "2", "3", "4")) : 
>  is.numeric(x) || is.logical(x) is not TRUE
>> var(c("1","2","3","4"),c("1","2","3","4") )
> [1] 1.666667
> 
> -pd
> 
> 
>> On 9 Jan 2020, at 14:49 , Marc Schwartz via R-devel <r-devel at r-project.org> wrote:
>> 
>> Jean-Luc,
>> 
>> Please keep the communications on the list, for the benefit of others, now and in the future, via the list archive. I am adding r-devel back here.
>> 
>> I can't speak to the rationale in some of these cases. As I noted, it may be (is likely) due to differing authors over time, and there may have been relevant use cases at the time that the code was written, resulting in the various checks. Presumably, the additional checks were not incorporated into the other functions to enforce a level of consistency.
>> 
>> We will need to wait for someone from R Core to comment.
>> 
>> Regards,
>> 
>> Marc
>> 
>>> On Jan 9, 2020, at 8:34 AM, Lipatz Jean-Luc <jean-luc.lipatz at insee.fr> wrote:
>>> 
>>> Ok, inconstencies.
>>> 
>>> The last test you wrote is a bit strange. I agree that it is useful to warn about a computation that have no sense in the case of factors. But why testing data;frames? If you go that way using random structures, you can also try :
>>> 
>>>> median(list(1,2),list(3,4),list(4,5))
>>> Error in if (na.rm) x <- x[!is.na(x)] else if (any(is.na(x))) return(x[FALSE][NA]) : 
>>> l'argument n'est pas interpr?table comme une valeur logique
>>> De plus : Warning message:
>>> In if (na.rm) x <- x[!is.na(x)] else if (any(is.na(x))) return(x[FALSE][NA]) :
>>> la condition a une longueur > 1 et seul le premier ?l?ment est utilis?
>>> 
>>> giving a message which, despite of his length, doesn't really explain the reason of the error.
>>> 
>>> Why not a test on arguments like?
>>> if (!is.numeric(x)) 
>>>        stop("need numeric data")
>>> 
>>> 
>>> -----Message d'origine-----
>>> De : Marc Schwartz <marc_schwartz at me.com> 
>>> Envoy? : jeudi 9 janvier 2020 14:19
>>> ? : Lipatz Jean-Luc <jean-luc.lipatz at insee.fr>
>>> Cc : R-Devel <r-devel at r-project.org>
>>> Objet : Re: [Rd] mean
>>> 
>>> 
>>>> On Jan 9, 2020, at 7:40 AM, Lipatz Jean-Luc <jean-luc.lipatz at insee.fr> wrote:
>>>> 
>>>> Hello,
>>>> 
>>>> Is there a reason for the following behaviour?
>>>>> mean(c("1","2","3"))
>>>> [1] NA
>>>> Warning message:
>>>> In mean.default(c("1", "2", "3")) :
>>>> l'argument n'est ni num?rique, ni logique : renvoi de NA
>>>> 
>>>> But:
>>>>> var(c("1","2","3"))
>>>> [1] 1
>>>> 
>>>> And also:
>>>>> median(c("1","2","3"))
>>>> [1] "2"
>>>> 
>>>> But:
>>>>> quantile(c("1","2","3"),p=.5)
>>>> Error in (1 - h) * qs[i] : 
>>>> argument non num?rique pour un op?rateur binaire
>>>> 
>>>> It sounds like a lack of symetry. 
>>>> Best regards.
>>>> 
>>>> 
>>>> Jean-Luc LIPATZ
>>>> Insee - Direction g?n?rale
>>>> Responsable de la coordination sur le d?veloppement de R et la mise en oeuvre d'alternatives ? SAS
>>> 
>>> 
>>> Hi,
>>> 
>>> It would appear, whether by design or just inconsistent implementations, perhaps by different authors over time, that the checks for whether or not the input vector is numeric differ across the functions.
>>> 
>>> A further inconsistency is for median(), where:
>>> 
>>>> median(c("1", "2", "3", "4"))
>>> [1] NA
>>> Warning message:
>>> In mean.default(sort(x, partial = half + 0L:1L)[half + 0L:1L]) :
>>> argument is not numeric or logical: returning NA
>>> 
>>> as a result of there being 4 elements, rather than 3, and the internal checks in the code, where in the case of the input vector having an even number of elements, mean() is used:
>>> 
>>>  if (n%%2L == 1L) 
>>>      sort(x, partial = half)[half]
>>>  else mean(sort(x, partial = half + 0L:1L)[half + 0L:1L])
>>> 
>>> 
>>> Similarly:
>>> 
>>>> median(factor(c("1", "2", "3")))
>>> Error in median.default(factor(c("1", "2", "3"))) : need numeric data
>>> 
>>> because the input vector is a factor, rather than character, and the initial check has:
>>> 
>>> if (is.factor(x) || is.data.frame(x)) 
>>>        stop("need numeric data")
>>> 
>>> 
>>> Regards,
>>> 
>>> Marc Schwartz
>>> 
>>> 
>> 
>> ______________________________________________
>> R-devel at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-devel
> 
> -- 
> 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
> 
> 
> 
> 
> 
> 
> 
> 
> 



[Rd] mean
Marc Schwartz