[R] intersect of list elements

From: Georg Otto <georg.otto_at_tuebingen.mpg.de>
Date: Sat 22 Jul 2006 - 03:39:09 EST

Hi,

i have a list of several vectors, for example:

> vectorlist

$vector.a.1
[1] "a" "b" "c"

$vector.a.2
[1] "a" "b" "d"

$vector.b.1
[1] "e" "f" "g"

I can use intersect to find elements that appear in $vector.a.1 and $vector.a.2:

> intersect(vectorlist[[1]], vectorlist[[2]])
[1] "a" "b"

I would like to use grep to get the vectors by their names matching an expression and to find the intersects between those vectors. For the first step:

> vectorlist[grep ("vector.a", names(vectorlist))]
$vector.a.1
[1] "a" "b" "c"

$vector.a.2
[1] "a" "b" "d"

Unfortunately, I can not pass the two vectors as argument to intersect:

> intersect(vectorlist[grep ("vector.a", names(vectorlist))])
Error in unique(y[match(x, y, 0)]) : argument "y" is missing, with no default

I am running R Version 2.3.1 (2006-06-01)

Could somone help me to solve this?

Cheers,

Georg



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