[R] how to skip NA columns ?

[Czerminski, Ryszard]

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]
   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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