R help - Jan 2008 - Delete Columns with zeros

Hi,

I know there have been some discussions on that topic. all their 
solutions failed in my case...
My problem is that I have a dataframe with many zeros. but while 
plotting they are not useful.
so I want to get rid of column 1,3,4,......,n i have 628 columns 1000 
rows, so I can?t look manually for the "empty" columns.

Any possible Ideas?

 > A250[1:5,1:4]

AAPU ACTO ACRA ADBA
A1100 0 0.0 0 0
A20100 0 0.1 0 0
A20200 0 0.0 0 0
A400 0 1.0 0 0
A4100 0 0.0 0 0

I also didn?t find anything useful in "An Introduction to R".

thank you

Jens

-- 
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Dipl.Biol. Jens Oldeland
University of Hamburg
Biocentre Klein Flottbek and Botanical Garden
Ohnhorststr. 18
22609 Hamburg,
Germany

Tel:    0049-(0)40-42816-407
Fax:    0049-(0)40-42816-543
Mail: 	Oldeland at botanik.uni-hamburg.de
        Jens.Oldeland at DLR.de  (for attachments > 2mb!!)
http://www.biologie.uni-hamburg.de/bzf/fbda005/fbda005.htm
+++++++++++++++++++++++++++++++++++++++++

Jens Oldeland wrote:
> Hi,
> 
> I know there have been some discussions on that topic. all their 
> solutions failed in my case...
> My problem is that I have a dataframe with many zeros. but while 
> plotting they are not useful.
> so I want to get rid of column 1,3,4,......,n i have 628 columns 1000 
> rows, so I can?t look manually for the "empty" columns.
> 
> Any possible Ideas?
> 
>  > A250[1:5,1:4]
> 
> AAPU ACTO ACRA ADBA
> A1100 0 0.0 0 0
> A20100 0 0.1 0 0
> A20200 0 0.0 0 0
> A400 0 1.0 0 0
> A4100 0 0.0 0 0
> 
> I also didn?t find anything useful in "An Introduction to R".
  A250[, sapply(A250, function(x) any(x))]
  A250[, apply(A250, 2, function(x) any(x))]

Uwe Ligges


> thank you
> 
> Jens
>

hits=-2.6 tests?YES_00
X-USF-Spam-Flag: NO

On Thu, 2008-01-31 at 15:33 +0100, Jens Oldeland wrote:
> Hi,
> 
> I know there have been some discussions on that topic. all their 
> solutions failed in my case...
> My problem is that I have a dataframe with many zeros. but while 
> plotting they are not useful.
> so I want to get rid of column 1,3,4,......,n i have 628 columns 1000 
> rows, so I can??t look manually for the "empty" columns.
> 
> Any possible Ideas?
> 
>  > A250[1:5,1:4]
> 
> AAPU ACTO ACRA ADBA
> A1100 0 0.0 0 0
> A20100 0 0.1 0 0
> A20200 0 0.0 0 0
> A400 0 1.0 0 0
> A4100 0 0.0 0 0
> 
> I also didn??t find anything useful in "An Introduction to R".
You can use colSums() to get the column sums and then evaluate which are
greater than 0, and keep only those.

## example data
> dat <- data.frame(x = rep(0, 10), y = runif(10), z = rep(0, 10), a =
rnorm(10))
> dat
   x          y z           a
1  0 0.49300402 0 -0.04405118
2  0 0.59786017 0 -2.06150000
3  0 0.08937639 0 -0.48804730
4  0 0.81220978 0  0.89746064
5  0 0.08846686 0  1.89563799
6  0 0.11141525 0 -0.16550292
7  0 0.25976990 0  1.02780712
8  0 0.55836579 0 -1.19074561
9  0 0.19798582 0  0.29130921
10 0 0.65826305 0  1.29665594
> colSums(dat)
       x        y        z        a 
0.000000 3.866717 0.000000 1.459024 
> colSums(dat) > 0
    x     y     z     a 
FALSE  TRUE FALSE  TRUE 
> dat[, colSums(dat) > 0]
            y           a
1  0.49300402 -0.04405118
2  0.59786017 -2.06150000
3  0.08937639 -0.48804730
4  0.81220978  0.89746064
5  0.08846686  1.89563799
6  0.11141525 -0.16550292
7  0.25976990  1.02780712
8  0.55836579 -1.19074561
9  0.19798582  0.29130921
10 0.65826305  1.29665594

HTH

G
> 
> thank you
> 
> Jens
> 
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