R help - Sep 2009 - What is the best way to get a subset of a data.frame?

Hi,

I want to construct a data.frame 'y' by using x$x and x$y. I think
that there might be better ways to do it (because, for example, we can
use a_matrix[3:5,] to extract certain rows, where 'a_matrix' is a
matrix). Can somebody let know what the best way is?
> a=data.frame(x=1:10,y=rep("abc",10),z=rep("xyz",10))
> a
    x   y   z
1   1 abc xyz
2   2 abc xyz
3   3 abc xyz
4   4 abc xyz
5   5 abc xyz
6   6 abc xyz
7   7 abc xyz
8   8 abc xyz
9   9 abc xyz
10 10 abc xyz
> b=data.frame(x=a$x, y=a$y)
> b
    x   y
1   1 abc
2   2 abc
3   3 abc
4   4 abc
5   5 abc
6   6 abc
7   7 abc
8   8 abc
9   9 abc
10 10 abc



Regards,
Peng

Hi Peng,
Take a look at Juliet Hannah's post at
http://www.nabble.com/correct-way-to-subset-a-vector-to24412577.html#a24412577
for
some alternatives.

<http://www.nabble.com/correct-way-to-subset-a-vector-to24412577.html#a24412577>
HTH,
Jorge


On Wed, Sep 16, 2009 at 10:14 PM, Peng Yu <> wrote:
> Hi,
>
> I want to construct a data.frame 'y' by using x$x and x$y. I think
> that there might be better ways to do it (because, for example, we can
> use a_matrix[3:5,] to extract certain rows, where 'a_matrix' is a
> matrix). Can somebody let know what the best way is?
>
> >
a=data.frame(x=1:10,y=rep("abc",10),z=rep("xyz",10))
> > a
>    x   y   z
> 1   1 abc xyz
> 2   2 abc xyz
> 3   3 abc xyz
> 4   4 abc xyz
> 5   5 abc xyz
> 6   6 abc xyz
> 7   7 abc xyz
> 8   8 abc xyz
> 9   9 abc xyz
> 10 10 abc xyz
> > b=data.frame(x=a$x, y=a$y)
> > b
>    x   y
> 1   1 abc
> 2   2 abc
> 3   3 abc
> 4   4 abc
> 5   5 abc
> 6   6 abc
> 7   7 abc
> 8   8 abc
> 9   9 abc
> 10 10 abc
>
>
>
> Regards,
> Peng
>
> ______________________________________________
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
	[[alternative HTML version deleted]]

Hi

r-help-bounces at r-project.org napsal dne 17.09.2009 04:14:24:
> Hi,
> 
> I want to construct a data.frame 'y' by using x$x and x$y. I think
> that there might be better ways to do it (because, for example, we can
> use a_matrix[3:5,] to extract certain rows, where 'a_matrix' is a
> matrix). Can somebody let know what the best way is?
> 
> >
a=data.frame(x=1:10,y=rep("abc",10),z=rep("xyz",10))
> > a
>     x   y   z
> 1   1 abc xyz
> 2   2 abc xyz
> 3   3 abc xyz
> 4   4 abc xyz
> 5   5 abc xyz
> 6   6 abc xyz
> 7   7 abc xyz
> 8   8 abc xyz
> 9   9 abc xyz
> 10 10 abc xyz
> > b=data.frame(x=a$x, y=a$y)
> > b
what is wrong on

b[1:2,]

Regards
Petr

>     x   y
> 1   1 abc
> 2   2 abc
> 3   3 abc
> 4   4 abc
> 5   5 abc
> 6   6 abc
> 7   7 abc
> 8   8 abc
> 9   9 abc
> 10 10 abc
> 
> 
> 
> Regards,
> Peng
> 
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide 
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.