Subset with time changes timezone

[eibanez]

I have found a strange behavior when using subset with dates. As you can see, the timezone in the datetime column changes. Winston also found this behavior on a Mac (https://groups.google.com/forum/#!topic/manipulatr/p39QNVQ8bUg).

I have not checked if the other verbs have a similar impact. Here is a small example, the results and my session info.

CODE

library(dplyr)
library(lubridate)

date.start <- ymd_hms("2014-01-01 00:00:00")
test <- data.frame(Date = date.start + hours(1:10))
test2 <- test %.% filter(Date < date.start + hours(5))

RESULTS

> test$Date[1:5]
[1] "2014-01-01 01:00:00 UTC" "2014-01-01 02:00:00 UTC" "2014-01-01 03:00:00 UTC"
[4] "2014-01-01 04:00:00 UTC" "2014-01-01 05:00:00 UTC"

> test2$Date[1:4]
[1] "2013-12-31 18:00:00 MST" "2013-12-31 19:00:00 MST" "2013-12-31 20:00:00 MST"
[4] "2013-12-31 21:00:00 MST"

SESSION INFO

> sessionInfo()
R version 3.0.2 (2013-09-25)
Platform: i386-w64-mingw32/i386 (32-bit)

locale:
[1] LC_COLLATE=English_United States.1252  LC_CTYPE=English_United States.1252   
[3] LC_MONETARY=English_United States.1252 LC_NUMERIC=C                          
[5] LC_TIME=English_United States.1252    

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

other attached packages:
[1] lubridate_1.3.1 dplyr_0.1      

loaded via a namespace (and not attached):
[1] assertthat_0.1 digest_0.6.4   memoise_0.1    plyr_1.8       Rcpp_0.10.6   
[6] stringr_0.6.2  tools_3.0.2

[hadley]

@romainfrancois I think this just means that you're not copying the tz attribute. In the case of grouped mutate or summary, the individual groups should return vectors which all have the same tz attribute, but it is possible that they might be different. In that case, I think the best thing you can do is issue a warning.