I just encountered another RTFM problem: With
diff(as.POSIXct(...), ...) I was unable to control the units of the
results. Examples:
> (d.d <- diff(as.POSIXct(c('2012-12-12', '2012-12-13'))))
Time difference of 1 days
> (d.h <- diff(as.POSIXct(c('2012-12-12 08:00', '2012-12-12 09:00'))))
Time difference of 1 hours
> (d.m <- diff(as.POSIXct(c('2012-12-12 08:00', '2012-12-12 08:01'))))
Time difference of 1 mins
> (d.s <- diff(as.POSIXct(c('2012-12-12 08:00:00', '2012-12-12
08:00:01'))))
Time difference of 1 secs
> as.numeric(d.d)
[1] 1
> as.numeric(d.s)
[1] 1
methods('diff') identified the following:
[1] diff.Date diff.default diff.POSIXt diff.ts diff.zoo*
In looking at the help pages for each of these functions, I found
no mention of "difftime" or any other way to control the units.
methods('-')
[1] -.Date -.POSIXt -.yearmon* -.yearqtr*
?"-.Date" didn't seem helpful on this, either. ?"-.POSIXt"
contained a link to "difftime", but I didn't see that until after I read
the code for "-.POSIXt" and found "difftime".
I humbly beseech ye to consider adding a difftime example to all
these help pages.
Thanks,
Spencer
p.s. In case there is any doubt, I very much appreciate all the work
that the R Core team has invested in making R what it is today.
--
Spencer Graves, PE, PhD
President and Chief Technology Officer
Structure Inspection and Monitoring, Inc.
751 Emerson Ct.
San José, CA 95126
ph: 408-655-4567
web: www.structuremonitoring.com
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