R help - Jun 2003 - date to age

I have files which have columns of data that look like this:

DOB
9/27/1964
...

That is, dates in month/day/year format.  When variables like DOB are read
in, they are converted to factors.

So, I wrote this to convert from date to age in years:

age<-function(x)
{as.numeric(Sys.time()-strptime(as.character(x),format="%m/%d/%Y"))/365.25}

This isn't very precise or pretty, but it works.

Does anybody have something better?

On Mon, 30 Jun 2003, William Briggs wrote:
> I have files which have columns of data that look like this:
> 
> DOB
> 9/27/1964
> ...
> 
> That is, dates in month/day/year format.  When variables like DOB are read
> in, they are converted to factors.
Why?  You can avoid that, of course.
> So, I wrote this to convert from date to age in years:
> 
> age<-function(x)
>
{as.numeric(Sys.time()-strptime(as.character(x),format="%m/%d/%Y"))/365.25}
> 
> This isn't very precise or pretty, but it works.
> 
> Does anybody have something better?
Convert to POSIXlt and compare differences in years, months, days etc.
Write an extension to difftime() to handle years and contribute it?

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
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