On Oct 12, 2010, at 1:40 PM, Bond, Stephen wrote:
Hello everybody,
Data is
myd <-
data.frame(id1=rep(c("a","b","c"),each=3),id2=rep(1:3,3),val=rnorm(9))
I want to get a cumulative sum over each of id1. trying aggregate
does not work
myd$pcum <- aggregate(myd[,c("val")],list(orig=myd$id1),cumsum)
Use ave instead of aggregate:
> ave(myd$val, list(myd$id1), FUN=cumsum)
[1] 0.362123399 -1.538797831 -2.061733393 -2.038050242 -0.344382401
-1.365281650
[7] 0.391181119 -0.258668053 -0.007736216
myd$pcum <- ave(myd$val, list(myd$id1), FUN=cumsum)
Please suggest a solution. In real the dataframe is huge so looping
with for and subsetting is not a great idea (still doable, though).
Thank you
Stephen B
--
David Winsemius, MD
West Hartford, CT
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