[R] sort (all columns of) a matrix

[William Dunlap]

> -----Original Message-----
> From: r-help-bounces at r-project.org 
> [mailto:r-help-bounces at r-project.org] On Behalf Of Bert Gunter
> Sent: Thursday, October 08, 2009 11:41 AM
> To: 'Erik Iverson'; 'Kajan Saied'; r-help at r-project.org
> Subject: Re: [R] sort (all columns of) a matrix
> 
> Right. My guess is that  Kajan wants:
> 
> a[do.call(order,data.frame(a)),] 
> ## this generalizes to an arbitrary number of columns
> ## do.call() is a very powerful and useful R feature worth 
> learning about

If you are compulsive wrap the second argument to do.call()
with unname(), just in case the data.frame has a column
with a name matching an argument to order (currently
'decreasing' and 'na.last').  This can save you from an
error like the following, where the 'decreasing' column
of 'd' is taken to be the 'decreasing' argument to order,
not just another column to sort:

  > d<-data.frame(weight=c(190, 121, 167, 121),
decreasing=c(TRUE,TRUE,FALSE,FALSE))
  > d[do.call(order,d),]
    weight decreasing
  1    190       TRUE
  3    167      FALSE
  2    121       TRUE
  4    121      FALSE
  > d[do.call(order,unname(d)),]
    weight decreasing
  4    121      FALSE
  2    121       TRUE
  3    167      FALSE
  1    190       TRUE

At some point data.frame may take more pains to make sure its
instances all have column names, in which case the argument needs
to be wrapped with unname(as.list(...)).

(Internally order() can call do.call("order",...) without using unname
so it could run into the same problem.)

Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com 
> 
> 
> Yet another reason why the posting guide asks for a simple, proper,
> reproducible example.
> 
> -- Bert
> 
> Bert Gunter
> Genentech Nonclinical Biostatistics
>  
>  
> 
> -----Original Message-----
> From: r-help-bounces at r-project.org 
> [mailto:r-help-bounces at r-project.org] On
> Behalf Of Erik Iverson
> Sent: Thursday, October 08, 2009 11:28 AM
> To: Kajan Saied; r-help at r-project.org
> Subject: Re: [R] sort (all columns of) a matrix
> 
> You need to define "sorted" in the context of a matrix.  By each row
> individually, by each column individually, or by column using 
> the whole
> matrix, or by row using the whole matrix? 
> 
> > -----Original Message-----
> > From: r-help-bounces at r-project.org 
> [mailto:r-help-bounces at r-project.org]
> > On Behalf Of Kajan Saied
> > Sent: Thursday, October 08, 2009 11:51 AM
> > To: r-help at r-project.org
> > Subject: [R] sort (all columns of) a matrix
> > 
> > Dear R-Help Team,
> > 
> > I have been trying to sort (all columns of) a matrix:
> > 
> > > a<-matrix(a<-c(1,3,4,6,6,4,6,56,4,64,86,39,4,2),length(a),2)
> > > a
> >       [,1] [,2]
> >  [1,]    1    1
> >  [2,]    3    3
> >  [3,]    4    4
> >  [4,]    6    6
> >  [5,]    6    6
> >  [6,]    4    4
> >  [7,]    6    6
> >  [8,]   56   56
> >  [9,]    4    4
> > [10,]   64   64
> > [11,]   86   86
> > [12,]   39   39
> > [13,]    4    4
> > [14,]    2    2
> > >
> > I would like to have the matrix sorted and the output 
> should again be *a
> > matrix* with nrow=length(a) and ncol=2 just like (a) but only
> > sorted. Whatever I try (be it sort(), order()...) I receive 
> a vector of
> > length(a)*2...
> > 
> > Could you please help me?
> > 
> > Best regards,
> > 
> > kajan
> > 
> > 	[[alternative HTML version deleted]]
> > 
> > ______________________________________________
> > 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.
> 
> ______________________________________________
> 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.
> 
> ______________________________________________
> 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.
>