From J.C.Rougier@durham.ac.uk  Tue Jan  4 16:17:33 2000
From: J.C.Rougier@durham.ac.uk (Jonathan Rougier)
Date: Tue, 4 Jan 2000 16:17:33 +0000 (GMT)
Subject: set functions
In-Reply-To: <x24sctg6bz.fsf@blueberry.kubism.ku.dk>
Message-ID: <Pine.GSO.4.20.0001041612590.20724-100000@laplace>

On 4 Jan 2000, Peter Dalgaard BSA wrote:

> > "equiv" <- function(x, y) all(c(match(x, y, 0)>0, match(y, x, 0)>0))

> length(setdiff(x,y))==0 appears to be about twice as fast....

But I don't think that would be right!

length(setdiff(1:4, 1:5))==0	# is TRUE
equiv(1:4, 1:5)			# clearly FALSE

Jonathan.

Jonathan Rougier                       Science Laboratories
Department of Mathematical Sciences    South Road
University of Durham                   Durham DH1 3LE

"[B]egin upon the precept ... that the things we see are to be 
 weighed in the scale with what we know"  (Meredith, 1879, The Egoist)

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set functions
Jonathan Rougier