Multiple unions

Question

I am trying to do unions on several lists (these are actually GRanges objects not integer lists but the priciple is the same), basically one big union.

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Answer 1

I think it would be cleaner to separate the "dereference" part from the n-ary union part, e.g.

dereflist <- function(l) lapply(a,get)
nunion <- function(l) Reduce(union,l)

But if you look at how union works, you'll see that you could also do

nunion <- function(l) unique(do.call(c,l))

which is faster in all the cases I've tested (much faster for long lists).

-s