Calculate ages in R

Question

I have two data frames in R. One frame has a persons year of birth:

YEAR
/1931
/1924

and then another column shows a more recent time.

Answer 1

I think this might be a bit more intuitive and requires no formatting or stripping:

as.numeric(as.Date("2002-02-02") - as.Date("1924-08-03")) / 365

gives output:

77.55342

Then you can use floor(), round(), or ceiling() to round to a whole number.

Answer 2

Based on the previous answer, convert your columns to date objects and subtract. Some conversion of types between character and numeric is necessary:

> foo=data.frame(RECENT=c("09/08/2005","11/08/2005"),YEAR=c("/1931","/1924"))
> foo
      RECENT  YEAR
1 09/08/2005 /1931
2 11/08/2005 /1924
> foo$RECENTd = as.Date(foo$RECENT, format="%m/%d/%Y")
> foo$YEARn = as.numeric(substr(foo$YEAR,2,999))
> foo$AGE = as.numeric(format(foo$RECENTd,"%Y")) - foo$YEARn
> foo
      RECENT  YEAR    RECENTd YEARn AGE
1 09/08/2005 /1931 2005-09-08  1931  74
2 11/08/2005 /1924 2005-11-08  1924  81

Note I've assumed you have that slash in your year column.

Also, tip for when asking questions about dates is to include a day that is past the twelfth so we know if you are a month/day/year person or a day/month/year person.