Hello!
na.encode does not have any effect on format of NA values of Date and
POSIXct (POSIXlt?) "atomic" classes in a data.frame. Here is the
example
(the same in R 2.3.1 and 2.5.0 (2006-09-19 r39409)):
testData <- data.frame(num=c(NA, 2.6),
int=c(1, NA),
fac=factor(c(NA, "abc")),
cha=c("a", NA),
dat=as.Date(c("1900-1-1", NA)),
POS=as.POSIXct(strptime(c("1900-1-1 01:01:01",
NA),
format="%Y-%m-%d %H:%M:%S")))
testData$cha <- as.character(testData$cha)
testData
num int fac cha dat POS
1 NA 1 <NA> a 1900-01-01 1900-01-01 01:01:01
2 2.6 NA abc <NA> <NA> <NA>
format(testData)
num int fac cha dat POS
1 NA 1 NA a 1900-01-01 1900-01-01 01:01:01
2 2.6 NA abc NA <NA> <NA>
^^^^ ^^^^
format(testData, na.encode=FALSE)
num int fac cha dat POS
1 NA 1 <NA> a 1900-01-01 1900-01-01 01:01:01
2 2.6 NA abc <NA> <NA> <NA>
format(testData, na.encode=TRUE)
num int fac cha dat POS
1 NA 1 NA a 1900-01-01 1900-01-01 01:01:01
2 2.6 NA abc NA <NA> <NA>
^^^^ ^^^^
After a brief look into format.data.frame, format.POSIXct and
format.POSIXlt I notice that na.encode is not used at all in (last line
of format.POSIXlt)
.Internal(format.POSIXlt(x, format, usetz))
but I get lost from this point forward. I guess that the same applies to
format.Date as this coerces Date to POSIXlt before formatting.
Additionally, I would suggest change in format help page for argument
na.encode. It says now
na.encode: logical: should 'NA' strings be encoded?
If I am not wrong, this applies only to non-numeric columns. Something
like the following might be more accurate:
na.encode: logical: should 'NA' strings be encoded (applies only to
non-numeric)?
--
Lep pozdrav / With regards,
Gregor Gorjanc
----------------------------------------------------------------------
University of Ljubljana PhD student
Biotechnical Faculty
Zootechnical Department URI: http://www.bfro.uni-lj.si/MR/ggorjan
Groblje 3 mail: gregor.gorjanc <at> bfro.uni-lj.si
SI-1230 Domzale tel: +386 (0)1 72 17 861
Slovenia, Europe fax: +386 (0)1 72 17 888
----------------------------------------------------------------------
"One must learn by doing the thing; for though you think you know it,
you have no certainty until you try." Sophocles ~ 450 B.C.
