Maybe this :
> foo <- function( x ){
+ idx <- 1 + cumsum( is.na( x ) )
+ not.na <- ! is.na( x )
+ split( x[not.na], idx[not.na] )
+ }
> foo( x )
$`1`
[1] 2 1 2
$`2`
[1] 1 1 2
$`3`
[1] 4 5 2 3
Romain
Le 29/04/10 09:42, Tal Galili a écrit :
Hi all,
I would like to have a function like this:
split.vec.by.NA<- function(x)
That takes a vector like this:
x<- c(2,1,2,NA,1,1,2,NA,4,5,2,3)
And returns a list of length of 3, each element of the list is the relevant
segmented vector, like this:
$`1`
[1] 2 1 2
$`2`
[1] 1 1 2
$`3`
[1] 4 5 2 3
I found how to do it with a loop, but wondered if there is some smarter
(vectorized) way of doing it.
Here is the code I used:
x<- c(2,1,2,NA,1,1,2,NA,4,5,2,3)
split.vec.by.NA<- function(x)
{
# assumes NA are seperating groups of numbers
#TODO: add code to check for it
number.of.groups<- sum(is.na(x)) + 1
groups.end.point.locations<- c(which(is.na(x)), length(x)+1) # This will be
all the places with NA's + a nubmer after the ending of the vector
group.start<- 1
group.end<- NA
new.groups.split.id<- x # we will replace all the places of the group with
group ID, excapt for the NA, which will later be replaced by 0
for(i in seq_len(number.of.groups))
{
group.end<- groups.end.point.locations[i]-1
new.groups.split.id[group.start:group.end]<- i
group.start<- groups.end.point.locations[i]+1 # make the new group start
higher for the next loop (at the final loop it won't matter
}
new.groups.split.id[is.na(x)]<- 0
return(split(x, new.groups.split.id)[-1])
}
split.vec.by.NA(x)
Thanks,
Tal
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Romain Francois
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http://romainfrancois.blog.free.fr
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