You can also use 'split' to separate each group: > split(d, list(d$a, d$c)) $`1.1` a b c n cum 1 1 1 1 11.1 11.1 6 1 2 1 12.1 23.2 11 1 3 1 13.1 36.3
$`2.1` a b c n cum 2 2 1 1 21.1 21.1 7 2 2 1 22.1 43.2 12 2 3 1 23.1 66.3 $`3.1` a b c n cum 3 3 1 1 31.1 31.1 8 3 2 1 32.1 63.2 13 3 3 1 33.1 96.3 $`4.1` a b c n cum 4 4 1 1 41.1 41.1 9 4 2 1 42.1 83.2 14 4 3 1 43.1 126.3 $`5.1` a b c n cum 5 5 1 1 51.1 51.1 10 5 2 1 52.1 103.2 15 5 3 1 53.1 156.3 $`1.2` a b c n cum 16 1 1 2 11.2 11.2 21 1 2 2 12.2 23.4 26 1 3 2 13.2 36.6 $`2.2` a b c n cum 17 2 1 2 21.2 21.2 22 2 2 2 22.2 43.4 27 2 3 2 23.2 66.6 $`3.2` a b c n cum 18 3 1 2 31.2 31.2 23 3 2 2 32.2 63.4 28 3 3 2 33.2 96.6 $`4.2` a b c n cum 19 4 1 2 41.2 41.2 24 4 2 2 42.2 83.4 29 4 3 2 43.2 126.6 $`5.2` a b c n cum 20 5 1 2 51.2 51.2 25 5 2 2 52.2 103.4 30 5 3 2 53.2 156.6 > On Tue, Dec 7, 2010 at 6:39 AM, Gerrit Draisma <gdrai...@xs4all.nl> wrote: > Dear R-users, > > I have a dataset with categories and numbers. > I would like to compute and add cumulative numbers > to the dataset. > I do not understand the structure of by(...) or > tapply(...) output enough to handle it. > > Here a small example > -------------- > d<-expand.grid(a=1:5,b=1:3,c=1:2) > d$n = 10 * d$a + d$b +0.1* d$c > Sn<-by(d$n,list(d$a,d$c),cumsum) > str(Sn) > --------- > List of 10 > $ : num [1:3] 11.1 23.2 36.3 > $ : num [1:3] 21.1 43.2 66.3 > $ : num [1:3] 31.1 63.2 96.3 > $ : num [1:3] 41.1 83.2 126.3 > $ : num [1:3] 51.1 103.2 156.3 > $ : num [1:3] 11.2 23.4 36.6 > $ : num [1:3] 21.2 43.4 66.6 > $ : num [1:3] 31.2 63.4 96.6 > $ : num [1:3] 41.2 83.4 126.6 > $ : num [1:3] 51.2 103.4 156.6 > - attr(*, "dim")= int [1:2] 5 2 > - attr(*, "dimnames")=List of 2 > ..$ : chr [1:5] "1" "2" "3" "4" ... > ..$ : chr [1:2] "1" "2" > - attr(*, "call")= language by.default(data = d$n, INDICES = list(d$a, > d$c), FUN = cumsum) > - attr(*, "class")= chr "by > --------- > # these give (a) lists of one numerical vector(a) > Sn[5,2] > Sn[cbind(d$a,d$c)] > # how to access the individual cumsum values? > # and assign them to d$Sn? > -------------- > > Thanks, > Gerrit. > > --- > Gerrit Draisma > Department of Public Health > Erasmus MC, University Medical Center Rotterdam > Room AE-235 > P.O. Box 2040 3000 CA Rotterdam The Netherlands > Phone: +31 10 7043787 Fax: +31 10 7038474 > http://mgzlx4.erasmusmc.nl/pwp/?gdraisma > > ______________________________________________ > 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 Data Munger Guru What is the problem that you are trying to solve? ______________________________________________ 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.
