[R] strange date problem - May 3, 1992 is NA

[David Winsemius]

On Jun 22, 2011, at 2:03 PM, Sarah Goslee wrote:

> Hi,
>
> On Wed, Jun 22, 2011 at 11:40 AM, Alexander Shenkin  
> <ashenkin at ufl.edu> wrote:
>>> is.na(strptime("5/2/1992", format="%m/%d/%Y"))
>> [1] FALSE
>>> is.na(strptime("5/3/1992", format="%m/%d/%Y"))
>> [1] TRUE
>
> I can't reproduce your problem on R 2.13.0 on linux:

I also cannot reproduce it on a Mac with 2.13.0 beta

 > is.na(strptime("5/3/1992", format="%m/%d/%Y"))
[1] FALSE
 > sessionInfo()
R version 2.13.0 beta (2011-04-04 r55296)
Platform: x86_64-apple-darwin9.8.0/x86_64 (64-bit)

locale:
[1] en_US.UTF-8/en_US.UTF-8/C/C/en_US.UTF-8/en_US.UTF-8

attached base packages:
[1] grid      splines   stats     graphics  grDevices utils     datasets
[8] methods   base

other attached packages:
  [1] reshape2_1.1        gplots_2.8.0        caTools_1.12
  [4] bitops_1.0-4.1      gdata_2.8.1         gtools_2.6.2
  [7] gamair_0.0-7        mgcv_1.7-6          Matrix_0.999375-50
[10] latticeExtra_0.6-16 RColorBrewer_1.0-2  rms_3.3-0
[13] Hmisc_3.8-3         survival_2.36-9     sos_1.3-0
[16] brew_1.0-6          lattice_0.19-26

loaded via a namespace (and not attached):
[1] cluster_1.13.3 nlme_3.1-101   plyr_1.5.2     stringr_0.4
[5] tools_2.13.0

>
>> strptime("5/2/1992", format="%m/%d/%Y")
> [1] "1992-05-02"
>> is.na(strptime("5/2/1992", format="%m/%d/%Y"))
> [1] FALSE
>> strptime("5/3/1992", format="%m/%d/%Y")
> [1] "1992-05-03"
>> is.na(strptime("5/3/1992", format="%m/%d/%Y"))
> [1] FALSE
>
> My suspicion is that you imported the data from a spreadsheet and
> there's some formatting glitch that's not showing up. If you type the
> string "5/3/1992" into the command by hand, do you still get the same
> result?
>
> If so, then we need to know your OS and version of R, at least.
>
>> Any idea what's going on with this?  Running strptime against all  
>> dates
>> from around 1946, only 5/3/1992 was converted as "NA".  Even  
>> stranger,
>> it still seems to have a value associated with it (even though is.na
>> thinks it's NA):
>>
>>> strptime("5/3/1992", format="%m/%d/%Y")
>> [1] "1992-05-03"
>
> This makes no sense to me.
>
> Sarah
>
>
> -- 
> Sarah Goslee
> http://www.functionaldiversity.org
>
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> and provide commented, minimal, self-contained, reproducible code.

David Winsemius, MD
West Hartford, CT