R devel - Feb 2009 - Bug in subsetting data frame (PR#13515)

Full_Name: Xin Lee
Version: 2.8.0
OS: Windows XP
Submission from: (NULL) (193.200.150.23)


Dear developer

I discover annoying bug in subsetting data frame.  Here is reproducable
examples:
> data.frame <- data.frame(x = runif(5), y = runif(5), row.names
c('a','b','c','d','e')
> subset <- data.frame['x']
> subset['a',]
work
> subset <- data.frame$x
> subset['a',]
not work
> subset <- data.frame['a',]
> subset[,'x']
work
> subset <- data.frame[,'x']
> subset['a',]
not work

I hope this is easy fix for you and works corectly soon.

Sincerely,
Xin Lee

On Tue, 10 Feb 2009 xinlee883 at stat.math.ethz.ch wrote:
>
> I discover annoying bug in subsetting data frame.  Here is reproducable
> examples:
These are not bugs.
>> data.frame <- data.frame(x = runif(5), y = runif(5), row.names >
c('a','b','c','d','e')
>
>> subset <- data.frame['x']
>> subset['a',]
> work
>
>> subset <- data.frame$x
>> subset['a',]
> not work
This can't possibly work, since you have explicitly requested that subset
not be a data frame.

There has been recent discussion about whether row names should be added as
names to vectors from a data frame, in which case subset['a'] would then
work. It doesn't now, and that isn't a bug either.
>> subset <- data.frame['a',]
>> subset[,'x']
> work
>
>> subset <- data.frame[,'x']
>> subset['a',]
> not work
This is also not a bug.  The drop= option to [ controls what happens when the
subset has dimensions of length 1. If you want subset to be a data frame in this
context, use
   subset <- data.frame[,'x',drop=FALSE]
and then subset['a',] will do want you want.

        -thomas

Thomas Lumley			Assoc. Professor, Biostatistics
tlumley at u.washington.edu	University of Washington, Seattle

Don't know if this is the problem, but....

It is a bad idea to set data.frame <- xxx since R has a single
namespace for functions and variables.

        -s

On 2/10/09, xinlee883 at stat.math.ethz.ch <xinlee883 at
stat.math.ethz.ch> wrote:
> Full_Name: Xin Lee
> Version: 2.8.0
> OS: Windows XP
> Submission from: (NULL) (193.200.150.23)
>
>
> Dear developer
>
> I discover annoying bug in subsetting data frame.  Here is reproducable
> examples:
>
>> data.frame <- data.frame(x = runif(5), y = runif(5), row.names >
c('a','b','c','d','e')
>
>> subset <- data.frame['x']
>> subset['a',]
> work
>
>> subset <- data.frame$x
>> subset['a',]
> not work
>
>> subset <- data.frame['a',]
>> subset[,'x']
> work
>
>> subset <- data.frame[,'x']
>> subset['a',]
> not work
>
> I hope this is easy fix for you and works corectly soon.
>
> Sincerely,
> Xin Lee
>
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>