From maechler@stat.math.ethz.ch  Tue Nov 21 15:15:19 2000
From: maechler@stat.math.ethz.ch (maechler@stat.math.ethz.ch)
Date: Tue, 21 Nov 2000 16:15:19 +0100 (MET)
Subject: [Rd] match() is not correct for "close numerics" (PR#741)
Message-ID: <200011211515.QAA10625@pubhealth.ku.dk>

(thank to  David James <dj@research.bell-labs.com> )

This is for R versions <= 1.1.1  and also R-devel as of yesterday..

  > pi0 <- pi + 2*.Machine$double.eps
  > pi != pi0
  [1] TRUE

  > ## but
  > match(c(1,pi,pi0), pi)
  [1] NA  1  1

The explanation is

  > match
  function(x, table, nomatch=NA)
      .Internal(match(as.character(x), as.character(table), nomatch))

and using

  > match <- function(x, table, nomatch=NA) .Internal(match(x, table, nomatch))

would solve the above problem
*but* gives new ones: e.g., factor() has to be modified !

Martin Maechler <maechler@stat.math.ethz.ch>	http://stat.ethz.ch/~maechler/
Seminar fuer Statistik, ETH-Zentrum  LEO D10	Leonhardstr. 27
ETH (Federal Inst. Technology)	8092 Zurich	SWITZERLAND
phone: x-41-1-632-3408		fax: ...-1228			<><

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[Rd] match() is not correct for "close numerics" (PR#741)
maechler@stat.math.ethz.ch