On Sat, 3 Sep 2016, Bert Gunter wrote:
Chuck et. al.:
As I said previously, my intuition about the relative efficiency of
tapply() and duplicated() in the context of this thread was wrong.
My `intuition' was wrong, too.
But tapply() uses split() which runs quite fast. So not a big surprise,
but if you look thru tapply() you'll notice it is well crafted in other
ways. In particular, the way the `f' arg of split is constructed makes a
big difference in timing (using a for loop to build up a mixed radix
number). In fact interaction(f,g) needs about 3 times the time of
tapply(f,list(f,g)) for just building an index.
Thanks for following up.
Best,
Chuck
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