[R] Vector indices and minus sign

Liaw, Andy
Fri, 14 Nov 2003 18:05:39 -0000

I guess what I suggested violates operator precedence rule.  It would only
work if somehow the subset operators can recognize the "-" first and
treat
whatever follows in a different way; i.e., to recognize that -numeric(0) is
NOT the same as numeric(0).  Oh well...

Andy

-----Original Message-----
From: Patrick Burns [mailto:pburns@pburns.seanet.com]
Sent: Friday, November 14, 2003 12:06 PM
To: Liaw, Andy
Cc: 'Thomas Lumley'; David Orme; r-help@stat.math.ethz.ch
Subject: Re: [R] Vector indices and minus sign




Liaw, Andy wrote:


From: Thomas Lumley [mailto:tlumley@u.washington.edu
<mailto:tlumley@u.washington.edu> ]



On Fri, 14 Nov 2003, David Orme wrote:





Hi,



I got caught out by this behaviour in 1.8.0 and I wondered why this

happens:





Some anomaly of this sort is unavoidable because R allows

positive or negative numeric indices. It can't distinguish

between a vector of no positive numbers and a vector of no

negative numbers.



	-thomas





I guess this can only work if "-" is treated specially in the subset

operators, so that, e.g., x[-"Andy"] would also work.  (This would be
nice,

IMHO.)

I agree that  x[-c("Andy", "Pat")] would come in handy at
times, but
x[-numeric(0)] still can not work because the numbers that aren't there
might be negative and the minus sign is to put them positive.

Pat




[A bit OT: I remembered that among the list of bugs fixed in Splus 3.2 for

Windows is -0 == 0 is F...]



Andy



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