WIll this do it for you:
> x <- read.table(textConnection("ColA ColB
+ 1 0
+ 3 0
+ 2 1
+ 2 0
+ 1 0
+ 4 0
+ 1 1
+ 9 1
+ 3 0
+ 5 0
+ 2 1"), header=TRUE)
> closeAllConnections()
> x.s <- split(x, cumsum(x$ColB))
> x.l <- do.call(rbind, lapply(x.s, function(.grp){
+ newdata <- cbind(.grp, sum=cumsum((.grp$ColB == 0) * .grp$ColA))
+ newdata$sum[newdata$ColB == 1] <- .001
+ newdata
+ }))
>
> x.l
ColA ColB sum
0.1 1 0 1.000
0.2 3 0 4.000
1.3 2 1 0.001
1.4 2 0 2.000
1.5 1 0 3.000
1.6 4 0 7.000
2 1 1 0.001
3.8 9 1 0.001
3.9 3 0 3.000
3.10 5 0 8.000
4 2 1 0.001
>
On Tue, Feb 9, 2010 at 9:06 PM, Kara Przeczek <przec...@unbc.ca> wrote:
> Dear R Help:
>
> I am trying to sum data from one column in a dataframe based on a value in
> another. I do not know how to do this easily in R.
> For example:
>
> Col A Col B
> 1 0
> 3 0
> 2 1
> 2 0
> 1 0
> 4 0
> 1 1
> 9 1
> 3 0
> 5 0
> 2 1
>
> I would like to cumsum the values in Col A for all rows where Col B is 0, and
> a value of 1 in Col B will reset the sum and give a value of 0.001. Thus, for
> this table I would like an output of 1, 4, 0.001, 2, 3, 7, 0.001, 0.001, 3,
> 8, 0.001.
> I tried using a For loop, but that summed all the Col A values together. I
> need something that does
> For (i in 1:length(df$Col B))
> {
> IF{Col B == 0, cumsum(Col A) "until" Col B == 1, else 0.001}
> }
> I don't know how to use "until" in R.
> Any help would be greatly appreciated!
> Kara
>
> ______________________________________________
> 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.
>
--
Jim Holtman
Cincinnati, OH
+1 513 646 9390
What is the problem that you are trying to solve?
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