# [R] union of lists

ggrothendieck@yifan.net ggrothendieck at yifan.net
Wed Apr 17 21:51:25 CEST 2002

```
Paste the lists together to create character strings and then parse them
back into R expressions and apply unique:

list1 <- list(c(1,34,5),c(2,1),c(3,10,15))
list2 <- list(c(1,5),c(2,1),c(3,10,29))

xx <- gsub("\\) *c\\(",",",paste(list1,list2))
xx <- sapply( xx , FUN=function(x)unique(eval(parse(text=x))) )

On 17 Apr 2002 at 15:24, Agustin Lobo wrote:

> Hi there,
>
> Given 2 lists of integer vectors, i.e.:
>
> > lista1
> \$"1"
> [1]  1 34  5
> \$"2"
> [1] 2 1
> \$"3"
> [1]  3 10 15
>
> > lista2
> \$"1"
> [1] 1 5
> \$"2"
> [1] 2 1
> \$"3"
> [1]  3 10 29
>
>
> I want to obtain the union of both, defined
> as the union of the vectors, that is
> lista.union[[1]] <- union(lista1[[1]],lista2[[1]]):
>
> > lista.union
> \$"1"
> [1]  1 34  5
> \$"2"
> [1] 2 1
> \$"3"
> [1]  3 10 15 29
>
> I'm now using a for loop and applying
> union() to each pair of vectors, but is
> there a faster way avoiding the for ?
>
> Thanks!
>
> Agus
>
>
> Dr. Agustin Lobo
> Instituto de Ciencias de la Tierra (CSIC)
> Lluis Sole Sabaris s/n
> 08028 Barcelona SPAIN
> tel 34 93409 5410
> fax 34 93411 0012
> alobo at ija.csic.es
>
>
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