[R] Bug in "transform"?

[Peter Dalgaard]

Prof Brian Ripley wrote:
> On Tue, 2 Dec 2008, Peter Dalgaard wrote:
> 
>> Prof Brian Ripley wrote:
>>> As the help page says
>>>
>>>      If some of the values are not vectors of the appropriate length,
>>>      you deserve whatever you get!
>>
>> Yes (did I write that?). It is a bit annoying with things that almost 
>> work, though.
>>
>>
>> [snip]
>>>
>>>> I often need to use this for creating new variables in data frame 
>>>> from those already present.
>>>> Sorely needed!!
>>>
>>> Just learn to use indexing: transform() is just syntactic sugar that 
>>> you are not making use of.
>>>
>>
>> ...at least when you're not making use of the scoping aspects. And if 
>> you calculate at least one vector of full length, then the issue goes 
>> away.
>>
>>
>>
>>> transform(aq, a=1,b=2)
>> Error in data.frame(`_data`, e[!matched]) :
>>  arguments imply differing number of rows: 6, 1
>>> transform(aq, a=1,b=2,o=Ozone)
>>    Ozone Solar.R Wind Temp Month Day a b  o
>> 3      12     149 12.6   74     5   3 1 2 12
>> 31     37     279  7.4   76     5  31 1 2 37
>> 34     NA     242 16.1   67     6   3 1 2 NA
>> 65     NA     101 10.9   84     7   4 1 2 NA
>> 59     NA      98 11.5   80     6  28 1 2 NA
>> 133    24     259  9.7   73     9  10 1 2 24
>>
>>
>>
>> The underlying issue is actually not in transform() but in data.frame():
> 
> Well, no, it is in the way that you call data.frame().  If you want to 
> add several variables, pass them as separate arguments rather than as a 
> list (just as they were passed to transform.data.frame).  That's a 
> simple change and will make transform.data.frame behave more 
> consistently with cbind.data.frame and data.frame.
> 

Hmm, you could well be right there. Not quite a simple spot change, 
though. As far as I see, either it needs do.call, or maybe there is a 
much more radical simplification possible. I'll have a look.

BTW, we have a deparser bug:

 > transform
function ("_data", ...)
UseMethod("transform")
<environment: namespace:base>

 > function ("_data", ...)
Error: unexpected string constant in "function ("_data""
....

 > f <- function (`_data`, ...) {}
 > attr(f,"source")<-NULL
 > f
function ("_data", ...)
{
}

It should deparse with backticks, not the old-style quotes (did that 
ever work?).

-- 
    O__  ---- Peter Dalgaard             Øster Farimagsgade 5, Entr.B
   c/ /'_ --- Dept. of Biostatistics     PO Box 2099, 1014 Cph. K
  (*) \(*) -- University of Copenhagen   Denmark      Ph:  (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)              FAX: (+45) 35327907