If Martin's proposal is accepted, does
that mean that the median method for
data frames would be something like:
function (x, ...)
{
stop(paste("you probably mean to use the command: sapply(",
deparse(substitute(x)), ", median)", sep=""))
}
Pat
On 29/04/2011 15:25, Martin Maechler wrote:
Paul Johnson<pauljoh...@gmail.com>
on Thu, 28 Apr 2011 00:20:27 -0500 writes:
> On Wed, Apr 27, 2011 at 12:44 PM, Patrick Burns
> <pbu...@pburns.seanet.com> wrote:
>> Here are some data frames:
>>
>> df3.2<- data.frame(1:3, 7:9)
>> df4.2<- data.frame(1:4, 7:10)
>> df3.3<- data.frame(1:3, 7:9, 10:12)
>> df4.3<- data.frame(1:4, 7:10, 10:13)
>> df3.4<- data.frame(1:3, 7:9, 10:12, 15:17)
>> df4.4<- data.frame(1:4, 7:10, 10:13, 15:18)
>>
>> Now here are some commands and their answers:
>>> median(df4.4)
>> [1] 8.5 11.5
>>> median(df3.2[c(1,2,3),])
>> [1] 2 8
>>> median(df3.2[c(1,3,2),])
>> [1] 2 NA
>> Warning message:
>> In mean.default(X[[2L]], ...) :
>> argument is not numeric or logical: returning NA
>>
>>
>>
>> The sessionInfo is below, but it looks
>> to me like the present behavior started
>> in 2.10.0.
>>
>> Sometimes it gets the right answer. I'd
>> be grateful to hear how it does that -- I
>> can't figure it out.
>>
> Hello, Pat.
> Nice poetry there! I think I have an actual answer, as opposed to the
> usual crap I spew.
> I would agree if you said median.data.frame ought to be written to
> work columnwise, similar to mean.data.frame.
> apply and sapply always give the correct answer
>> apply(df3.3, 2, median)
> X1.3 X7.9 X10.12
> 2 8 11
[...........]
exactly
> mean.data.frame is now implemented as
> mean.data.frame<- function(x, ...) sapply(x, mean, ...)
exactly.
My personal oppinion is that mean.data.frame() should never have
been written.
People should know, or learn, to use apply functions for such a
task.
The unfortunate fact that mean.data.frame() exists makes people
think that median.data.frame() should too,
and then
var.data.frame()
sd.data.frame()
mad.data.frame()
min.data.frame()
max.data.frame()
...
...
all just in order to *not* to have to know sapply()
????
No, rather not.
My vote is for deprecating mean.data.frame().
Martin
--
Patrick Burns
pbu...@pburns.seanet.com
twitter: @portfolioprobe
http://www.portfolioprobe.com/blog
http://www.burns-stat.com
(home of 'Some hints for the R beginner'
and 'The R Inferno')
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