Removing multiple elements from a vector or list
On Apr 15, 2013, at 2:30 PM, arun wrote:
Hi, vec1<- letters
alp <- as.list(letters) would have constructed the vector that was described.
vec1[!grepl("b|r|x",alp)]
# [1] "a" "c" "d" "e" "f" "g" "h" "i" "j" "k" "l" "m" "n" "o" "p" "q" "s" "t" "u"
#[20] "v" "w" "y" "z"
vec1[!vec1%in% c("b","r","x") ]
# [1] "a" "c" "d" "e" "f" "g" "h" "i" "j" "k" "l" "m" "n" "o" "p" "q" "s" "t" "u"
#[20] "v" "w" "y" "z"
alp<-lapply(seq_along(vec1),function(i) vec1[i])
res<-alp[!grepl("b|r|x",alp)]
unlist(res)
# [1] "a" "c" "d" "e" "f" "g" "h" "i" "j" "k" "l" "m" "n" "o" "p" "q" "s" "t" "u"
#[20] "v" "w" "y" "z"
unlist(alp[!alp%in%c("b","r","x")])
#[1] "a" "c" "d" "e" "f" "g" "h" "i" "j" "k" "l" "m" "n" "o" "p" "q" "s" "t" "u"
#[20] "v" "w" "y" "z"
A.K.
All good. There would be an additional way to do this if the list were first assigned names. (At the moment the list only has positions for reference.)
alp <- setNames(alp, letters[1:26])
# Something like that initial code would succeed:
alp <- alp[ !names(alp) %in% c("b","r","x")]
The result is still a list.
If I for example have a list (or vector) that contains all the letters in the alphabet.
alp <- list("a","b","c",......................."z") this is of course not the exact code
How can I remove multiple elements at one time without knowing their location in the list. Say I want to remove b,r,x?
Same question if apl is a vector
I have tried
alp <- alp[-c("b","r","x")]
You _cannot_use_negative_indexing_with_names (or values). You could have used logical indexing:
alp [ sapply(alp, function(x) !x %in% c("b","r","x") ) ]
# OR perhaps the most compact solution offered so far; numeric indexing with the minus unary operator:
alp[ -grep("b|r|x", alp) ]
David Winsemius Alameda, CA, USA