as.Date from 'YYYY.mm' format [duplicate]

Question

I have a data frame where date is stored as a double e.g., 1993.09 1993.10 1993.11 1993.12

I want to convert this into a date format '%Y %m %d' (with days always 1).

As far as I understand, as.Date() wants a string input. However, for some reason when I convert my dates into string sapply(dates, as.character) the zeros after ones disappear, effectively converting October to January, resulting into two Januaries per year.

dates
1993.07 1993.08 1993.09 1993.10 1993.11 1993.12
sapply(dates, as.character)
sub("[.]", " ", dates)
"1993 07" "1993 08" "1993 09" "1993 1"  "1993 11" "1993 12"

Is there a more straightforward way of converting the dates? Or where do I mess up?

dput:

c(1993.01, 1993.02, 1993.03, 1993.04, 1993.05, 1993.06, 1993.07, 
1993.08, 1993.09, 1993.1, 1993.11, 1993.12)

Answer 1

Your problem is that you have something that is a character string, but looks like a numeric and you didn't take care of this during import. R doesn't distinguish between 1993.1 and 1993.10. Both are the same number. Thus, as.character(1993.10) returns "1993.1". You need to use a formating function to make sure that you get two digits after the period, because to as.Date "1993.1" and "1993.01" are the same month.

x <- c(1993.09, 1993.10, 1993.11, 1993.12)
as.Date(sprintf("%.2f.01", x), format = "%Y.%m.%d")
#[1] "1993-09-01" "1993-10-01" "1993-11-01" "1993-12-01"

Of course, x should be imported as a character to begin with.