On Mon, 2 Nov 2009, Phil Smith wrote:
Hi R Community:
I want to take the difference in two dates:
dt2 - dt1.
But, I want the answer in months between those 2 dates.
Can you advise me?
How long is a month?
difftime() can give you an answer in days, which might suffice if you
define a month as a number of days. Another idea is to use (untested)
getMonth <- function(x)
{
xx <- as.POSIXlt(x)
12*xx$year + xx$mon + (xx$mday-1)/31
}
which will convert to a (fractional) number of months since
1900-01-01, and that can be differenced.
Please respond to: p...@cdc.gov
Thank you!
Phil Smith
Centers for Disease Control and Prevention
--
Brian D. Ripley, rip...@stats.ox.ac.uk
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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