Time data

Dear All, I wonder how to compute the age from the date of birth and the date of examination. Suppose that have the following data:

 df <- as.data.frame(rbind(c(1,"10/08/1950","15/03/1998"), c(1,"10/08/1950","20/07/1998"), c(1,"10/08/1950","23/10/1998")))

 names(df) <- c("ID", "date_birth", "date_exam")

 where:
 date_birth: is the date of birth
 date_exam: date of examination

 I used the following program to compute the value of the age  :

 difftime(strptime(as.character(df$date_exam), '%d/%m/%Y'), strptime(as.character(df$date_birth), '%d/%m/%Y'))/365.25

 which gives me as an output:

Time differences of 47.59491, 47.94251, 48.20260 days

 theses values are actually the 3 ages (but

 My questions are:

 1- Why in the output it says "days" instead of "years")

 2- How can I obtain the output as a numeric vector, without the statement "Time difference of ....". This is in order to use it in my calculations.

 3- Is there a way quicker and less redondant  to compute the age form the date_birth and date_exam?

 Thanks a lot,

 Bernard,



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