Hi
On 20 Dec 2005 at 11:12, Marc Bernard wrote: Date sent: Tue, 20 Dec 2005 11:12:28 +0100 (CET) From: Marc Bernard <[EMAIL PROTECTED]> To: r-help@stat.math.ethz.ch Subject: [R] 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") this is in attributes of an output and is not changed by calculations > > 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. as.numeric(as.Date(df$date_exam)-as.Date(df$date_birth))/365 However you can use it in calculations without problem as I suppose that "Time difference of" results from print method of a difftime object. > > 3- Is there a way quicker and less redondant to compute the age > form the date_birth and date_exam? as.Date(df$date_exam)-as.Date(df$date_birth) HTH Petr > > Thanks a lot, > > Bernard, > > > > --------------------------------- > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help@stat.math.ethz.ch mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide! > http://www.R-project.org/posting-guide.html Petr Pikal [EMAIL PROTECTED] ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html