Hi List,

I'm trying to work out how to use which(), or another function, to find the
top-level index of a list item based on a condition. An example will clarify
my question.

a <- list(c(1,2),c(3,4))
a
[[1]]
[1] 1 2

[[2]]
[1] 3 4

I want to find the top level index of c(1,2), which should return 1 since;

a[[1]]
[1] 1 2

I can't seem to work out the syntax. I've tried;

which(a == c(1,2))

and an error about coercing to double is returned. I can find the index of
elements of a particular item by

which(a[[1]]==c(1,2)) or which(a[[1]]==1) etc that return [1] 1 2 and [1] 1
respectively as they should. Any thoughts?

C

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