I noticed that Gabor's interpretation of your desires was the opposite
of what mine was, and also that you were thinking tapply might be a
useful strategy. Here is a tapply implementation that lets you choose:
x$wanted <- c(0,-diff(x$status))
x$dif.tm <- c(diff(x$time),NA)
sum(x[x$wanted==1, "dif.tm"], na.rm=TRUE)
# [1] 43
with( x, tapply(dif.tm, wanted, sum, na.rm=TRUE) )
# -1 0 1
# 26 6 43
On Jul 3, 2009, at 9:21 AM, rory.wins...@gmail.com wrote:
Hi
I have a dataset that looks like this (dput'd below):
head(x, 20)
time status
1 2009-07-02 10:32:37 1
snip
I would like to be able to calculate the total time spent in state
0, in
other words
the diff of the times of x where x$status changes from 0 to 1. I've
been
struggling
with tapply() to do this, but without huge success....anyone know an
elegant way
to do this?
Cheers
-- Rory
structure(list(time = structure(c(1246527157, 1246527163, 1246527163,
1246527164, 1246527164, 1246527168, 1246527168, 1246527174,
1246527184,
1246527184, 1246527185, 1246527187, 1246527193, 1246527197,
1246527220,
1246527228, 1246527230, 1246527231, 1246527232, 1246527232), class =
c("POSIXt",
"POSIXct"), tzone = ""), status = c(1, 0, 1, 0, 1, 0, 1, 0, 1,
0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0)), .Names = c("time", "status"
), row.names = c(NA, 20L), class = "data.frame")
David Winsemius, MD
Heritage Laboratories
West Hartford, CT
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
