[R] Union of list elements

[Gabor Grothendieck]

Patrick Meyer <patrick.meyer <at> internet.lu> writes:

: 
: Thank you Gabor.
: 
: But I have a problem with the beginning of my algorithm, where the list 
: you call L is empty... then the code breaks down... It says:
: 
: "Error in any(...,na.rm = na.rm) : incorrect argument type"
: 
: How can I handle this?
: 

Good point.  We can rescue it by doing the simplification ourself
using unlist(lapply(...)) instead of sapply(...):

L <- list()
newentry <- c("a3", "a1", "a4")
if (!any(unlist(lapply(L, setequal, newentry)))) L <- c(L, list(newentry))