R help - Jan 2012 - drop columns whose rows are all 0

Hello,
I have a dataset with 40 variables, some of them are always 0 (each 
row). I would like to make a subset containing only the columns which 
values are not all 0, but I don't know how to do it.

I tried:

for(cut_column in 1:40) {

if(sum(dataset[,cut_column])!=0) {
				columns_useful<-c(columns_useful,dataset[cut_column])

}
}

sorted_dataset<-subset(dataset, select=columns_useful)

But it doesn't work.
Thank you

Francisco

> dataset<-data.frame(a=1:10,b=c(0,0,0,1,0,0,0,0,1,0),c=rep(0,10))
> apply(dataset,2,function(x) all(x==0))
    a     b     c
FALSE FALSE  TRUE
> dataset[,!apply(dataset,2,function(x) all(x==0))]
    a b
1   1 0
2   2 0
3   3 0
4   4 1
5   5 0
6   6 0
7   7 0
8   8 0
9   9 1
10 10 0




On Tue, Jan 24, 2012 at 8:14 AM, Francisco
<franciscororolaio@google.com>wrote:
> Hello,
> I have a dataset with 40 variables, some of them are always 0 (each row).
> I would like to make a subset containing only the columns which values are
> not all 0, but I don't know how to do it.
>
> I tried:
>
> for(cut_column in 1:40) {
>
> if(sum(dataset[,cut_column])!=**0) {
>                                columns_useful<-c(columns_**
> useful,dataset[cut_column])
>
> }
> }
>
> sorted_dataset<-subset(**dataset, select=columns_useful)
>
> But it doesn't work.
> Thank you
>
> Francisco
>
> ______________________________**________________
> R-help@r-project.org mailing list
>
https://stat.ethz.ch/mailman/**listinfo/r-help<https://stat.ethz.ch/mailman/listinfo/r-help>
> PLEASE do read the posting guide http://www.R-project.org/**
> posting-guide.html <http://www.R-project.org/posting-guide.html>
> and provide commented, minimal, self-contained, reproducible code.
>
	[[alternative HTML version deleted]]

Try also

dataset[, colSums(dataset == 0) != nrow(dataset)]

HTH,
Jorge.-


On Tue, Jan 24, 2012 at 11:14 AM, Francisco <> wrote:
> Hello,
> I have a dataset with 40 variables, some of them are always 0 (each row).
> I would like to make a subset containing only the columns which values are
> not all 0, but I don't know how to do it.
>
> I tried:
>
> for(cut_column in 1:40) {
>
> if(sum(dataset[,cut_column])!=**0) {
>                                columns_useful<-c(columns_**
> useful,dataset[cut_column])
>
> }
> }
>
> sorted_dataset<-subset(**dataset, select=columns_useful)
>
> But it doesn't work.
> Thank you
>
> Francisco
>
> ______________________________**________________
> R-help@r-project.org mailing list
>
https://stat.ethz.ch/mailman/**listinfo/r-help<https://stat.ethz.ch/mailman/listinfo/r-help>
> PLEASE do read the posting guide http://www.R-project.org/**
> posting-guide.html <http://www.R-project.org/posting-guide.html>
> and provide commented, minimal, self-contained, reproducible code.
>
	[[alternative HTML version deleted]]

dataset.1 <- dataset[, apply(dataset, 2, sum)>0]

Gregorio R. Serrano

2012/1/24 Francisco <franciscororolaio@google.com>
> Hello,
> I have a dataset with 40 variables, some of them are always 0 (each row).
> I would like to make a subset containing only the columns which values are
> not all 0, but I don't know how to do it.
>
> I tried:
>
> for(cut_column in 1:40) {
>
> if(sum(dataset[,cut_column])!=**0) {
>                                columns_useful<-c(columns_**
> useful,dataset[cut_column])
>
> }
> }
>
> sorted_dataset<-subset(**dataset, select=columns_useful)
>
> But it doesn't work.
> Thank you
>
> Francisco
>
> ______________________________**________________
> R-help@r-project.org mailing list
>
https://stat.ethz.ch/mailman/**listinfo/r-help<https://stat.ethz.ch/mailman/listinfo/r-help>
> PLEASE do read the posting guide http://www.R-project.org/**
> posting-guide.html <http://www.R-project.org/posting-guide.html>
> and provide commented, minimal, self-contained, reproducible code.
>


-- 
Dr. Gregorio R. Serrano
Dpto. Economía Cuantitativa (UCM)
Voz:+34 91394 2361
Twitter: @grserrano_
http://www.grserrano.es

	[[alternative HTML version deleted]]

On 25/01/12 05:14, Francisco wrote:
> Hello,
> I have a dataset with 40 variables, some of them are always 0 (each 
> row). I would like to make a subset containing only the columns which 
> values are not all 0, but I don't know how to do it.
>
> I tried:
>
> for(cut_column in 1:40) {
>
> if(sum(dataset[,cut_column])!=0) {
>                 columns_useful<-c(columns_useful,dataset[cut_column])
>
> }
> }
>
> sorted_dataset<-subset(dataset, select=columns_useful)
>
> But it doesn't work.
Try:

     good_dataset <- dataset[,sapply(dataset,function(x){!all(x==0)})]

This works modulo possible gotchas induced by floating point arithmetic.

Another possibility:

     tol <- sqrt(.Machine$double.eps)
     good_dataset <- 
dataset[,sapply(dataset,function(x){!all(abs(x)<=tol)})]

Or:

     good_dataset <- 
dataset[,sapply(dataset,function(x){!isTRUE(all.equal(x,rep(0,length(x))))})]

The foregoing could trip up if some columns of "dataset" have extra 
attributes tagging
along.  E.g. the column could actually be a numeric matrix of zeroes --- 
in which case
it wouldn't get dropped.

     cheers,

         Rolf Turner

Another way would be a which statement. 

good_dataset=data[,which(colSums(data)!=0)]

I believe this depends on how the data are structured though. 


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