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

[John Kane]

I think I understand this.  Try
str(input) and you will see that input$disk2 in a
vector.  You can force a data.frame using 
data.frame(input(,targets))


--- "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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