Hi Gregor,
before even considering methods for "list" and "data.frame",
can you explain why you think it is important for levels() to
become a generic function at all?
For me, levels belong to factors (or then to contour plots, or
co-plots ) but exactly because level is a too generic word, it
seems to me to be problematic as a generic function.
How would describe the purpose of the levels() generic?
>>>>> "Gregor" == Gregor Gorjanc <[EMAIL PROTECTED]>
>>>>> on Mon, 20 Mar 2006 23:27:21 +0100 writes:
Gregor> oops, this does not pass R CMD check. I will have to read manuals a
bit
Gregor> more.
Gregor> ...
Gregor> * checking S3 generic/method consistency ... WARNING
Gregor> levels:
Gregor> function(x, ...)
Gregor> levels.list:
Gregor> function(x, drop)
Gregor> levels:
Gregor> function(x, ...)
Gregor> levels.data.frame:
Gregor> function(x, drop)
Gregor> ...
Gregor> Anyway, I would like to ask what is the "opinion" about writing
methods
Gregor> for classes as list and data.frame. Methods for this might not be as
Gregor> simple as for numeric, character, factor and it would be nice that
there
Gregor> would be some guidelines for at least:
Gregor> - what should be the "general" output i.e. list or something else -
I
Gregor> understand that it is hard to say in advance, but a common policy
might
Gregor> not hurt
Gregor> - what to do if a method for a list or data.frame can not be
applied to
Gregor> each entry/column
>> Hello!
>>
>> Does R core find the following pacth usefull - I created methods for
>> levels for list and data.frame, which can be usefull to get a list of
>> levels for entries in a list or columns in a data.frame. Patch is
>> attached and shown bellow example
>>
>> # Example
>>> tmp <- list()
>>> tmp$a <- factor(letters[1:10])
>>> tmp$b <- factor(letters[5:14])
>>> tmp$c <- 1:10
>>> tmp1 <- as.data.frame(tmp)
>>> tmp2 <- list()
>>> tmp2$"1" <- tmp
>>> tmp2$"2" <- tmp1
>>> str(tmp2)
>> List of 2
>> $ 1:List of 3
>> ..$ a: Factor w/ 10 levels "a","b","c","d",..: 1 2 3 4 5 6 7 8 9 10
>> ..$ b: Factor w/ 10 levels "e","f","g","h",..: 1 2 3 4 5 6 7 8 9 10
>> ..$ c: int [1:10] 1 2 3 4 5 6 7 8 9 10
>> $ 2:`data.frame': 10 obs. of 3 variables:
>> ..$ a: Factor w/ 10 levels "a","b","c","d",..: 1 2 3 4 5 6 7 8 9 10
>> ..$ b: Factor w/ 10 levels "e","f","g","h",..: 1 2 3 4 5 6 7 8 9 10
>> ..$ c: int [1:10] 1 2 3 4 5 6 7 8 9 10
>>
>>> levels(tmp2)
>> $"1"
>> $"1"$a
>> [1] "a" "b" "c" "d" "e" "f" "g" "h" "i" "j"
>>
>> $"1"$b
>> [1] "e" "f" "g" "h" "i" "j" "k" "l" "m" "n"
>>
>>
>> $"2"
>> $"2"$a
>> [1] "a" "b" "c" "d" "e" "f" "g" "h" "i" "j"
>>
>> $"2"$b
>> [1] "e" "f" "g" "h" "i" "j" "k" "l" "m" "n"
>>
>>> levels(tmp2, drop = FALSE)
>> $"1"
>> $"1"$a
>> [1] "a" "b" "c" "d" "e" "f" "g" "h" "i" "j"
>>
>> $"1"$b
>> [1] "e" "f" "g" "h" "i" "j" "k" "l" "m" "n"
>>
>> $"1"$c
>> NULL
>>
>>
>> $"2"
>> $"2"$a
>> [1] "a" "b" "c" "d" "e" "f" "g" "h" "i" "j"
>>
>> $"2"$b
>> [1] "e" "f" "g" "h" "i" "j" "k" "l" "m" "n"
>>
>> $"2"$c
>> NULL
>>
>> ----------------------------------------------------------------------
>>
>> $ svn diff factor.R
>> Index: factor.R
>> ===================================================================
>> --- factor.R (revision 37559)
>> +++ factor.R (working copy)
>> @@ -25,7 +25,25 @@
>> ## Help old S users:
>> category <- function(...) .Defunct()
>>
>> -levels <- function(x) attr(x, "levels")
>> +levels <- function(x, ...) UseMethod("levels")
>> +
>> +levels.default <- function(x, ...) attr(x, "levels")
>> +
>> +levels.list <- function(x, drop = TRUE)
>> +{
>> + tmp <- lapply(x, levels, drop = drop)
>> + if (drop) {
>> + tmp1 <- unlist(lapply(tmp, is.null))
>> + tmp <- tmp[!tmp1]
>> + }
>> + return(tmp)
>> +}
>> +
>> +levels.data.frame <- function(x, ...)
>> +{
>> + return(levels.list(x, ...))
>> +}
>> +
>> nlevels <- function(x) length(levels(x))
>>
>> "levels<-" <- function(x, value) UseMethod("levels<-")
>>
Gregor> --
Gregor> Lep pozdrav / With regards,
Gregor> Gregor Gorjanc
Gregor>
----------------------------------------------------------------------
Gregor> University of Ljubljana PhD student
Gregor> Biotechnical Faculty
Gregor> Zootechnical Department URI:
http://www.bfro.uni-lj.si/MR/ggorjan
Gregor> Groblje 3 mail: gregor.gorjanc <at> bfro.uni-lj.si
Gregor> SI-1230 Domzale tel: +386 (0)1 72 17 861
Gregor> Slovenia, Europe fax: +386 (0)1 72 17 888
Gregor>
----------------------------------------------------------------------
Gregor> "One must learn by doing the thing; for though you think you know
it,
Gregor> you have no certainty until you try." Sophocles ~ 450 B.C.
Gregor> ______________________________________________
Gregor> R-devel@r-project.org mailing list
Gregor> https://stat.ethz.ch/mailman/listinfo/r-devel
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