Re: [R] Check values in colums matrix

From: Berton Gunter <gunter.berton_at_gene.com>
Date: Fri 25 Aug 2006 - 09:37:16 EST


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).

> -----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
> >
> > ______________________________________________
> > 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.
> >
>
> ______________________________________________
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> PLEASE do read the posting guide
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> and provide commented, minimal, self-contained, reproducible code.
>



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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 10:51:32 2006

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