From: <Bill.Venables_at_csiro.au>

Date: Fri 25 Aug 2006 - 13:39:48 EST

R-help@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. Received on Fri Aug 25 13:50:54 2006

Date: Fri 25 Aug 2006 - 13:39:48 EST

constantColmuns <- function(Xmat)

which(apply(Xmat, 2, function(z) length(unique(z)) == 1))

> -----Original Message-----

*> From: r-help-bounces@stat.math.ethz.ch
*

[mailto:r-help-bounces@stat.math.ethz.ch] On Behalf Of Berton Gunter

*> Sent: Friday, 25 August 2006 9:37 AM
*

> To: 'Gabor Grothendieck'; 'Muhammad Subianto'

*> Cc: r-help@stat.math.ethz.ch
**> Subject: Re: [R] Check values in colums matrix
**>
**> Absolutely. But do note that if the values in obj are the product of
**> numerical computations then columns of equal values may turn out to be
*

only

> **nearly** equal and so the sd may turn out to be **nearly** 0 and not

*> exactly 0. This is a standard issue in numerical computation, of
*

course, and

> has been commented on in this list at least dozens of times, but it's

still

> a gotcha for the unwary (so now dozens +1).

*>
**> -- Bert Gunter
**> Genentech Non-Clinical Statistics
**> South San Francisco, CA
**>
**>
**>
**> > -----Original Message-----
**> > From: r-help-bounces@stat.math.ethz.ch
**> > [mailto:r-help-bounces@stat.math.ethz.ch] On Behalf Of Gabor
**> > Grothendieck
**> > Sent: Thursday, August 24, 2006 4:28 PM
**> > To: Muhammad Subianto
**> > Cc: r-help@stat.math.ethz.ch
**> > Subject: Re: [R] Check values in colums matrix
**> >
**> > Try sd(obj.tr) which will give a vector of standard
**> > deviations, one per column.
**> > A column's entry will be zero if and only if all values in the
*

column

> > are the same.

*> >
**> > On 8/24/06, Muhammad Subianto <msubianto@gmail.com> wrote:
**> > > Dear all,
**> > > I apologize if my question is quite simple.
**> > > I have a dataset (20 columns & 1000 rows) which
**> > > some of columns have the same value and the others
**> > > have different values.
**> > > Here are some piece of my dataset:
**> > > obj <- cbind(c(1,1,1,4,0,0,1,4,-1),
**> > > c(0,1,1,4,1,0,1,4,-1),
**> > > c(1,1,1,4,2,0,1,4,-1),
**> > > c(1,1,1,4,3,0,1,4,-1),
**> > > c(1,1,1,4,6,0,1,5,-1),
**> > > c(1,1,1,4,6,0,1,6,-1),
**> > > c(1,1,1,4,6,0,1,7,-1),
**> > > c(1,1,1,4,6,0,1,8,-1))
**> > > obj.tr <- t(obj)
**> > > obj.tr
**> > > > obj.tr
**> > > [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9]
**> > > [1,] 1 1 1 4 0 0 1 4 -1
**> > > [2,] 0 1 1 4 1 0 1 4 -1
**> > > [3,] 1 1 1 4 2 0 1 4 -1
**> > > [4,] 1 1 1 4 3 0 1 4 -1
**> > > [5,] 1 1 1 4 6 0 1 5 -1
**> > > [6,] 1 1 1 4 6 0 1 6 -1
**> > > [7,] 1 1 1 4 6 0 1 7 -1
**> > > [8,] 1 1 1 4 6 0 1 8 -1
**> > > >
**> > >
**> > > How can I do to check columns 2,3,4,6,7 and 9 have
**> > > the same value, and columns 1,5 and 8 have different values.
**> > >
**> > > Best, Muhammad Subianto
*

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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. Received on Fri Aug 25 13:50:54 2006

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