Hi All,
I have a vector n, and for each n[i] I want to extract n[i], n[i+1],
n[i+2]..., until the cumulative sum of n[i] and subsequent elements exceeds
a CheckValue, whereupon I move to the next index and repeat.
I am trying to find a Vectorized approach, and have seen similar posts where
filter{stat} and rollmean{zoo} were suggested, but, I haven't been able to
figure a way to use them for this problem.
Best wishes to all, and thanks for the help!
Dgnn
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Dgnn wrote:> > I have a vector n, and for each n[i] I want to extract n[i], n[i+1], > n[i+2]..., until the cumulative sum of n[i] and subsequent elements > exceeds a CheckValue, whereupon I move to the next index and repeat. > > I am trying to find a Vectorized approach, and have seen similar posts > where filter{stat} and rollmean{zoo} were suggested, but, I haven't been > able to figure a way to use them for this problem. > >Your quest for "move to the next index and repeat" only makes sense when the vector can be negative, so there might be several indexes where the crossing occurs. However, there is an additional assumptions that there was really a crossing; or, alternatively, that cumsum was below threshold in between. Here is a version that uses "diff" (Check: the index might be off-by one) Dieter set.seed(4711) vec = rnorm(100) cumsum(vec) thresh = 4 which(diff(cumsum(vec)<thresh)==1) -- View this message in context: http://n4.nabble.com/Extract-vector-elements-until-cumsum-x-tp998023p998155.html Sent from the R help mailing list archive at Nabble.com.
Try this which uses 10 as the check value: f <- function(acc, x) if (acc + x > 10) x else acc + x x <- c(4, 6, 2, 7, 4, 1, 4, 8) Reduce(f, x) On Sun, Jan 3, 2010 at 10:02 PM, Dgnn <sharkbrainpdx at gmail.com> wrote:> > Hi All, > > I have a vector n, and for each n[i] I want to extract n[i], n[i+1], > n[i+2]..., until the cumulative sum of n[i] and subsequent elements exceeds > a CheckValue, whereupon I move to the next index and repeat. > > I am trying to find a Vectorized approach, and have seen similar posts where > filter{stat} and rollmean{zoo} were suggested, but, I haven't been able to > figure a way to use them for this problem. > > Best wishes to all, and thanks for the help! > > Dgnn > > > -- > View this message in context: http://n4.nabble.com/Extract-vector-elements-until-cumsum-x-tp998023p998023.html > Sent from the R help mailing list archive at Nabble.com. > > ______________________________________________ > R-help at 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. >
Thanks a lot, everybody! I've been working with these data for a while, and didn't realize that some of my assumptions lead me to leave out some important info. Specifically, that the vector contains time values of intervals between adjacent events, and so are always positive. Thanks again for your help Dgnn -- View this message in context: http://n4.nabble.com/Extract-vector-elements-until-cumsum-x-tp998023p998420.html Sent from the R help mailing list archive at Nabble.com.