as.Date woes
Never mind... the solution was to read the source code of as.Date.character. It turns out the default format="" is meaningless. If 'format' is not given in the call to as.Date, it is NOT assumed to be "", and the function gives very different results from a call where the argument format="" is given. Grrrr... Peter On Wed, Aug 20, 2014 at 11:56 AM, Peter Langfelder
<peter.langfelder at gmail.com> wrote:
Hi all,
I have recently started working with Date objects and find the
experience unsettling, to put it mildly.
The help for as.Date says, in part:
## S3 method for class 'character'
as.Date(x, format = "", ...)
x: An object to be converted.
format: A character string. If not specified, it will try
?"%Y-%m-%d"? then ?"%Y/%m/%d"? on the first non-?NA? element,
and give an error if neither works.
If I read this correctly,
as.Date("2012-04-30") and
as.Date("2012-04-30", format = "")
should give the same results, but they don't:
as.Date("2012-04-30")
[1] "2012-04-30"
as.Date("2012-04-30", format = "")
[1] "2014-08-20" Note the latter gives today's date, without any warning or message. What method is called in the latter case? Another issue I am running into, that is probably connected to the 'format' argument above, is trying to convert a numeric or character in the same call. Basically, I would like to call as.Date(object, format = "", origin = "1970-1-1") where object can be a Date, numeric or character, in the hope that the appropriate method will be selected and will ignore unnecessary arguments. Here's what I get:
as.Date( as.numeric(Sys.Date()), origin = "1970-1-1")
[1] "2014-08-20" #### Correct
as.Date( as.numeric(Sys.Date()), origin = "1970-1-1", format = "")
[1] "2059-04-08" #### ??? Excuse the coarse language, but WTF??? The first call confirms that the origin is specified correctly, and the second gives a date removed from the origin by twice the number of days than the actual input??
as.numeric(Sys.Date())
[1] 16302
as.numeric(as.Date( as.numeric(Sys.Date()), origin = "1970-1-1"))
[1] 16302
as.numeric(as.Date( as.numeric(Sys.Date()), origin = "1970-1-1", format = ""))
[1] 32604 Thanks in advance for any pointers! Peter PS: I know my R is not the most up to date, but I haven't found anything about Date mentioned in the changelog for the 3.x series.
sessionInfo()
R version 3.0.2 Patched (2013-10-08 r64039) Platform: x86_64-unknown-linux-gnu (64-bit) locale: [1] LC_CTYPE=en_US.utf8 LC_NUMERIC=C [3] LC_TIME=en_US.utf8 LC_COLLATE=en_US.utf8 [5] LC_MONETARY=en_US.utf8 LC_MESSAGES=en_US.utf8 [7] LC_PAPER=en_US.utf8 LC_NAME=C [9] LC_ADDRESS=C LC_TELEPHONE=C [11] LC_MEASUREMENT=en_US.utf8 LC_IDENTIFICATION=C attached base packages: [1] stats graphics grDevices utils datasets methods base