CODEWITHSUNDEEP
r
Barnaby
Barnaby

Reputation: 1480

extracting common elements from a list and a vector in a list form

I have a list which contains different elements and a vector which list some of the elements, I would like to find out in which list index number does each element fall into. 

x <- list ( c ( 1,2 ), c( 3,4 ), c( 5,6 ), c( 7,8 ), c( 9,10 ) , c( 11,12 ))
y <- c( 2,3,4,6,8,10,11,12 )

# Desired Output in a list 

[[1]]
[1] 2

[[2]]
[1] 3 4

[[3]]
[1] 6

[[4]]
[1] 8

[[5]]
[1] 10

[[6]]
[1] 11 12

If both were two vectors I would use intersect and which as to find out the possition in x of elements in y

Upvotes: 0

Views: 290

Answers (2)

SuaveIncompetence
SuaveIncompetence

Reputation: 513

lapply combined with %in% will get you the answer:

lapply(x,function(i){i[i%in%y]})

lapply applies the function to each list element of 'x', the %in% evaluates whether each element of 'i' is in 'y'.

Upvotes: 1

thelatemail
thelatemail

Reputation: 93813

Use Map or lapply

Map(intersect, x, list(y))
#or
lapply(x, intersect, y)

#[[1]]
#[1] 2
#
#[[2]]
#[1] 3 4
#
#[[3]]
#[1] 6
#
#[[4]]
#[1] 8
#
#[[5]]
#[1] 10
#
#[[6]]
#[1] 11 12

Upvotes: 2

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