[R] using which to select range of values

[Steve Lianoglou]

Hi,

On Thu, Apr 22, 2010 at 11:21 AM, Muhammad Rahiz
<muhammad.rahiz at ouce.ox.ac.uk> wrote:
> Hi all,
>
> I would like to get the array index for a range of values, say  0 < x < 1.5.
> I'm wondering if there is an alternative for the following which I've done
>
> x0 <- rnorm(100)
> x1 <- ifelse(x0 > 0 & x0 < 1.5,"t","f")
> x2 <- which(x1=="t",arr.ind=TRUE)
> x0[x2]

Two things:

1. Not that it really matters, but why are you using arr.ind=TRUE when
x0 is just a "normal" vector?

2. Just skip the middle-man creation of x1:

R> x0 <- rnorm(100)
R> x2 <- which(x0 > 0 & x0 < 1.5)
R> x0[x2]

Why not just skip the middle man (x1)?

-- 
Steve Lianoglou
Graduate Student: Computational Systems Biology
 | Memorial Sloan-Kettering Cancer Center
 | Weill Medical College of Cornell University
Contact Info: http://cbio.mskcc.org/~lianos/contact