Why is parsing “%Y-%m” using strptime in R giving an NA result, but “%Y-%m-%d” works? [duplicate]

Answer 1

That seems like sensible behavior to me. As I see it, a better question would be "why does it allow you to do this: strptime("2009-03",format="%Y-%d")?"

Here's a workaround to get what I think you're trying to achieve (i.e. a POSIXlt object with a specified month and year, but today's day):

as.POSIXlt(paste("2009-12", days(Sys.Date()), sep="-"))

Answer 2

I'm just guessing here. But if it takes a year and a day, it's probably taking a year and a day in the range of 1-365 (or 366 for leap years). What you could do is use paste() and add -01 at the end to get the standard YYYY-MM-DD format.

Here's the test I ran.

strptime("2009-123",format="%Y-%d")

returns "2009-05-12"