[R] Is this a bug with a simple arithmetic operation with a vector object?

[Prof Brian D Ripley]

On Sun, 1 Apr 2001, hzi wrote:

> Hello-
>
>     While I was reading a tutorial book for R (actually, for S-Plus:Brian S. Everitt. A Handbook of Statistical Analysis using S-PLUS. Chapman & Hall, London, 1994) I tried to execute this simple exercise:
>
>         > x <- -c(1,2,3,4,5,6)
>     > X <- -c(10,11,12,100,-5,-6)
>     >x+X
>     [1] -11, -13, -15, -104, 0, 0
>
>     As you can see, the added vectors resulted in negative numbers !
(the answer should have been: [1] 11, 13, 15, 104, 0, 0)

Why?  Everitt's book is extremely badly typeset, and `< -'  is in fact `<-'
not `<- -' as you have entered.  But the laws of arithmetic say R was right.

>     Mind you, this is R 1.2.1 for Windows, under WIndows ME, 64 Mb RAM, pIII 800 MHz. The same thing happens, however, with the recently distributed "R 1.2.2 patched".

Why `mind you'?  A phrase involving `workmen' and `tools' springs to mind.

>     Clues, anyone?

Find a more reliable (and less outdated) guide ....

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272860 (secr)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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