R: strptime() and is.na () unexpected results
datetime, r, strptime
Solution
The problem is likely that all the times that return `NA` do not exist in whatever timezone you're using, due to daylight saving time.
Check with the data source to determine the timezone the data were recorded in, then set the `tz` argument to that value in your call to `strptime`.
Problem
I have a data frame with roughly 8 million rows and 3 columns. I used `strptime()` in the following manner: ``` df$date.time <- strptime(df$date.time, "%m/%d/%y %I:%M:%S %p") ``` This works fine for all but 1104 of the rows, which I checked using ``` df[is.na(df$date.time), ] ``` When I look at these "problem" data, the `date.time` entries seem to be formatted in the way I would expect. For example, here is an observation that comes up as a problem, but doesn't appear to be an NA: ``` id date.time outcome observation543490 2012-03-11 02:14:01 C ``` What could possibly be going on here that `is.na(df$date.time)` returns a TRUE value for this row that has apparently been converted correctly? Here's a reproducible example (if you're in CST): ``` is.na(strptime("03/11/12 2:14:01 AM", "%m/%d/%y %I:%M:%S %p", "CST6CDT")) #[1] TRUE ```