CODEWITHSUNDEEP
rlistfunctionloopslapply
rnorouzian
rnorouzian

Reputation: 7517

Deleting elements that appear only once in a list of vectors in R

I have a list of 3 vectors, X, Y, and Z. I was wondering how I could delete elements that appear only once (here ChandlerA and Trus.Hsu) across all 3 vectors?

d = list(X = c(Bit.KnoA = 4, Bit.KnoB = 1, Bit.KnoC = 2, ChandlerA = 3, Ellis.etal =4, 
               Mubarak=5, SheenA=6,  Shin.Ellis=7 , Sun = 8, Trus.Hsu=3 ), 

         Y = c(Bit.KnoA = 6, Bit.KnoB = 3, Bit.KnoC = 4, Ellis.etal =1, Mubarak=2, 
              SheenA=1,  Shin.Ellis=2 , Sun = 1),

         Z = c(Bit.KnoB = 2) )

Upvotes: 3

Views: 474

Answers (2)

thelatemail
thelatemail

Reputation: 93813

You could also use duplicated since you're only interested in the loner values:

nms <- unlist(lapply(d, names))
keep <- nms[duplicated(nms)]
lapply(d, function(x) x[names(x) %in% keep] )

#$X
#  Bit.KnoA   Bit.KnoB   Bit.KnoC Ellis.etal    Mubarak     SheenA Shin.Ellis        Sun 
#         4          1          2          4          5          6          7          8 
#
#$Y
#  Bit.KnoA   Bit.KnoB   Bit.KnoC Ellis.etal    Mubarak     SheenA Shin.Ellis        Sun 
#         6          3          4          1          2          1          2          1 
#
#$Z
#Bit.KnoB 
#       2

Upvotes: 3

Ronak Shah
Ronak Shah

Reputation: 388947

We could create a copy of d, remove it's names so that when we unlist the names of the list names are not prepended to the vector. Count number of occurrence of each name in the list and select names of those who occur only once and remove them from original list (d).

d1 <- d
names(d1) <- NULL
vals <- table(names(unlist(d1)))
delete_names <- names(vals[vals == 1])
lapply(d, function(x) x[setdiff(names(x), delete_names)])

#$X
#  Bit.KnoA   Bit.KnoB   Bit.KnoC Ellis.etal    Mubarak     SheenA Shin.Ellis        Sun 
#         4          1          2          4          5          6          7          8 

#$Y
#  Bit.KnoA   Bit.KnoB   Bit.KnoC Ellis.etal    Mubarak     SheenA Shin.Ellis        Sun 
#         6          3          4          1          2          1          2          1 

#$Z
#Bit.KnoB 
#       2

Upvotes: 3

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