[R] how to skip NA columns ?

[Prof Brian D Ripley]

On Thu, 20 Jun 2002, Czerminski, Ryszard wrote:

> It works for me for data frame very nicely, but I am not quite sure how to
> get it
> to work for a matrix ?
>
> R
>
> > df
>   V1 V2 V3
> 1  1 NA  7
> 2  2 NA  8
> 3  3 NA  9
> > mask <- sapply(df, function(x) any(is.na(x)))
> > df[!mask]
>   V1 V3
> 1  1  7
> 2  2  8
> 3  3  9
> > m <- as.matrix(df)
> > m
>   V1 V2 V3
> 1  1 NA  7
> 2  2 NA  8
> 3  3 NA  9
> > mask <- apply(m, 2, function(x) any(is.na(x)))
> > m[!mask]

m[, !mask] is needed: `matrix indexing'

>    1    3 <NA> <NA> <NA> <NA>
>    1    3   NA   NA    7    9
> > dim(m[!mask])
> NULL
> >
>
>
>
> Ryszard Czerminski   phone: (781)994-0479
> ArQule, Inc.         email:ryszard at arqule.com
> 19 Presidential Way  http://www.arqule.com
> Woburn, MA 01801     fax: (781)994-0679
>
>
> -----Original Message-----
> From: Prof Brian D Ripley [mailto:ripley at stats.ox.ac.uk]
> Sent: Thursday, June 20, 2002 8:14 AM
> To: Czerminski, Ryszard
> Cc: r-help at stat.math.ethz.ch
> Subject: Re: [R] how to skip NA columns ?
>
>
> Columns of what?  A data frame or a matrix?
>
> For a data frame DF
>
> hasna <- sapply(DF, function(x) any(is.na(x)))
> DF <- DF[!hasna]
>
> and `hasna' tells which you removed.  Use apply and matrix indexing for a
> matrix.
>
> On Thu, 20 Jun 2002, Czerminski, Ryszard wrote:
>
> > R-helpers!
> >
> > na.omit() can be used to remove rows with NA's
> > but how can I remove columns ? and remember, which columns have been
> removed
> > ?
> >
> > I guess I can do t(na.omit(t(o))) as shown below, but this probably
> creates
> > a lot of overhead and I do not know which columns
> > have been removed.
>
> It only works for matrices, too.
>
> > Yours,
> >
> > R
> >
> > > o
> >      [,1] [,2] [,3]
> > [1,]    1   NA    7
> > [2,]    2   NA    8
> > [3,]    3   NA    9
> > > t(na.omit(t(o)))
> >      [,1] [,2]
> > [1,]    1    7
> > [2,]    2    8
> > [3,]    3    9
> >
> > Ryszard Czerminski   phone: (781)994-0479
> > ArQule, Inc.         email:ryszard at arqule.com
> > 19 Presidential Way  http://www.arqule.com
> > Woburn, MA 01801     fax: (781)994-0679
> >
> >
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>
> --
> Brian D. Ripley,                  ripley at stats.ox.ac.uk
> Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
> University of Oxford,             Tel:  +44 1865 272861 (self)
> 1 South Parks Road,                     +44 1865 272860 (secr)
> Oxford OX1 3TG, UK                Fax:  +44 1865 272595
>
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-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272860 (secr)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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