R help - Nov 2006 - Sorting a data frame when you don't know the columns

Hi
 
Sorry to ask such a well oiled question, but even with multiple google hits I
don't think this has been answered very well.
 
It's all well and good doing a sort of a data frame on multiple columns when
you know in advance which columns you want to sort on, but what about when the
names of the columns you wish to sort on are in a vector?
 
At the minute I'm messing about with paste() to form a string that works for
order() and then calling do.call().  Is this really the best way of doing it?
 
Thanks
Mick

DF <- data.frame(a = c(3, 4, 2, 3, 2, 4, 2), b = 7:1))
DF[do.call(order, DF),]

will sort on all the columns.

On 11/28/06, michael watson (IAH-C) <michael.watson at bbsrc.ac.uk>
wrote:
> Hi
>
> Sorry to ask such a well oiled question, but even with multiple google hits
I don't think this has been answered very well.
>
> It's all well and good doing a sort of a data frame on multiple columns
when you know in advance which columns you want to sort on, but what about when
the names of the columns you wish to sort on are in a vector?
>
> At the minute I'm messing about with paste() to form a string that
works for order() and then calling do.call().  Is this really the best way of
doing it?
>
> Thanks
> Mick
>
> ______________________________________________
> R-help at stat.math.ethz.ch 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.
>

try this:

dat <- data.frame(x = rnorm(100), y = sample(rep(1:2, each = 50)), z = 
sample(rep(1:4, 25)))
#########
nams <- c("y", "z")
dat[do.call(order, dat[nams]), ]


I hope it helps.

Best,
Dimitris

----
Dimitris Rizopoulos
Ph.D. Student
Biostatistical Centre
School of Public Health
Catholic University of Leuven

Address: Kapucijnenvoer 35, Leuven, Belgium
Tel: +32/(0)16/336899
Fax: +32/(0)16/337015
Web: http://med.kuleuven.be/biostat/
     http://www.student.kuleuven.be/~m0390867/dimitris.htm


----- Original Message ----- 
From: "michael watson (IAH-C)" <michael.watson at bbsrc.ac.uk>
To: <r-help at stat.math.ethz.ch>
Sent: Tuesday, November 28, 2006 11:45 AM
Subject: [R] Sorting a data frame when you don't know the columns

> Hi
>
> Sorry to ask such a well oiled question, but even with multiple 
> google hits I don't think this has been answered very well.
>
> It's all well and good doing a sort of a data frame on multiple 
> columns when you know in advance which columns you want to sort on, 
> but what about when the names of the columns you wish to sort on are 
> in a vector?
>
> At the minute I'm messing about with paste() to form a string that 
> works for order() and then calling do.call().  Is this really the 
> best way of doing it?
>
> Thanks
> Mick
>
> ______________________________________________
> R-help at stat.math.ethz.ch 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.
> 

Disclaimer: http://www.kuleuven.be/cwis/email_disclaimer.htm