[6376] in s-news-athena
Re: Indices corresponding to a condition
daemon@ATHENA.MIT.EDU (Martin Maechler)
Fri Feb 3 10:16:21 1995
From: Martin Maechler <maechler@stat.math.ethz.ch>
Date: Fri, 3 Feb 1995 11:29:58 +0100
To: wand@agsm.unsw.edu.au
Cc: s-news@utstat.toronto.edu
In-Reply-To: <9502030620.AA16211@magic> (wand@agsm.unsw.edu.au)
Reply-To: Martin Maechler <maechler@stat.math.ethz.ch>
>>>>> "wand" == wand <wand@agsm.unsw.edu.au> writes:
wand> How does one find the indices of the entries of an array that
wand> satisfy a certain condition?
wand> For example, suppose
wand> a <- c(0.34,0.56,0.12,0.67,0.98,0.41)
wand> and you want the indices of those entries of "a" that are between
wand> 0.2 and 0.8;
wand> i.e. you want to obtain the array with entries
wand> 1 2 4 6
wand> Is there an easy way to do this?
Yes,
## A useful function :
which <- function(logi) seq(logi)[logi]
which( .2 < a & a < .8 )
or directly
seq(a)[.2 < a & a < .8]
Martin Maechler <maechler@stat.math.ethz.ch> <>< _
Seminar fuer Statistik, SOL F5 _| |_
ETH (Federal Inst. Technology) 8092 Zurich SWITZERLAND |_ _|
phone: x-41-1-632-3408 fax: ...-1086 |_|
