From tlumley@u.washington.edu  Thu Jan 17 00:30:08 2002
From: tlumley@u.washington.edu (tlumley@u.washington.edu)
Date: Thu, 17 Jan 2002 01:30:08 +0100 (MET)
Subject: [Rd] hashing NaN (PR#1267)
Message-ID: <200201170030.BAA20702@pubhealth.ku.dk>


Different NaNs can hash to different values and so be treated differently
by duplicated(), unique(), match(). Any IEEE double value with exponent
bits all 1 is NaN (except the one that is NA).

AFAICT all arithmetic and mathematical operations in R produce the same
NaN, but this is not guaranteed by any standard. read.spss() will produce
different NaNs when reading missing values in at least some circumstances.


	-thomas

Thomas Lumley			Asst. Professor, Biostatistics
tlumley@u.washington.edu	University of Washington, Seattle


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[Rd] hashing NaN (PR#1267)
tlumley@u.washington.edu