CODEWITHSUNDEEP
rlistsearchvector
betabandido
betabandido

Reputation: 19704

Searching for a vector in a list

This might seem like a silly question, but after spending some time looking for an (easy) solution, I could not find it.

I have a list of vectors:

l <- list(c(1, 2), c(5, 10))

and I want to test whether a given vector --- for instance, c(1, 2) --- is in that list. I thought the "straightforward" approach would work:

c(1, 2) %in% l

but that returns

[1] FALSE FALSE

In the end I found the following solution:

any(sapply(l, function(x) { all(x == c(1, 2)) }))

but it is quite cumbersome, so I really wonder if that is the simplest option. Is there any simpler way to test for a vector in a list of vectors?

Upvotes: 1

Views: 79

Answers (1)

Se&#241;or O
Se&#241;or O

Reputation: 17412

Since you are dealing with objects the == operator is not ideal. A slightly simpler approach is:

any(sapply(l, identical, y=c(1,2)))

The %in% operator doesn't work because it is a call to the function match. It reads l as a vector. In other words, what it's doing is:

for(i in 1:length(c(1,2)))
c(1,2)[i]==l[[i]]

Upvotes: 3

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