[R] Aggregating by a grouping

Moshe Olshansky m_olshansky at yahoo.com
Thu Dec 20 13:29:42 CET 2007


One possibility is:

> x
[1] "A" "B" "C" "D" "A" "C" "D" "B"
> y
[1] 10 11  9  8 12  4  5  7
> basic_map
[[1]]
[1] "A" "B"

[[2]]
[1] "C" "D"

> a <- which(sapply(basic_map,function(u) x %in%
u),arr.ind=TRUE)
> aggregate(y,list(a[order(a[,1]),2]),sum)
  Group.1  x
1       1 40
2       2 26
> 

--- "Kondamani, Arjun (GMI - NY Corporate Bonds)"
<arjun_kondamani at ml.com> wrote:

> Suppose I have:
> 
> Book	Value	
> A	10	
> B	11	
> C	9	
> D	8	
> A	12	
> C	4	
> D	5	
> B	7	
> 
> I want to summarize above not by Book but by
> groupings of Books as in
> (below)
> 
> I have a list ... basic_map <-
> list(c("A",B"),c("C,D"))
> Big_names <- c("A1", "A2")
> Names(basic_map) <- big_names
> 
> So I want to get :
> 
> A1 40
> A2 26
> 
> How do I use tapply AND the list to get my custom
> groupings?
> 
> thx
>
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