[R] Subsetting a data.frame degenerates at one column?

[jim holtman]

try:

input[,targets, drop=FALSE]

see:

?"["

for an explanation.


On 2/8/08, Allen S. Rout <asr at ufl.edu> wrote:
>
> Greetings.
>
> At the moment, I'm applying R to some AIX 'nmon' output, trying to get
> a handle on some disk performance metrics.  In case anyone's
> interested:
>
> http://docs.osg.ufl.edu/tsm/pdf/
>
> some of them are more edifying than others. (ahem)
>
> I'm trying to develop a somewhat general framework for plotting these
> measures, in the hopes that it's of some use to people other than me.
> One obstacle I encounter is that, when I select one column out of a
> data.frame, the result is no longer a data.frame.  So, say I've got,
> in data frame 'input'
>
>      disk1 disk2 disk3 disk4
> T0000     0     1     0     4
> T0001     0     1     0     5
> T0002     0     1     0     5
> T0003     0     2     0     4
> T0004     0     2     0     3
> T0005     0     1     0     3
> T0006     0     0     0     3
>
> and somewhere I've noted a list
>
> targets <- c('disk2','disk3')
>
> I can say
>
> input[,targets]
>      disk2 disk3
> T0000     1     0
> T0001     1     0
> T0002     1     0
> T0003     2     0
> T0004     2     0
> T0005     1     0
> T0006     0     0
>
> but if
>
> targets <- c('disk2')
> input[,targets]
> [1] 1 1 1 2 2 1 0
>
> Ick.
>
> I've been reading through the indexing and data.frame docs, and remain
> unsatisfied so far.  Where is my thinking going wrong?
>
>
>
> - Allen S. Rout
>
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>


-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem you are trying to solve?