R help - Jul 2008 - Remove non-numerical columns from data frame

Hello,

My question sounds simple, but as I am desperatly searchin for a solution I am 
asking you all. :)

I try to filter out all non-numeric columns of a data frame using a for loop 
to go through all columns. My if clause looks like this:

        for(j in 1:length(data)) {

                ...
                if(!is.numeric(data[j])) skip <- "not numeric")
                ...
        }

When I do: is.numeric(data$vol) i get TRUE as result:
unfortunately this is not applicable in a for loop, because i need to go 
through all of the columns using j. 
I also tried to paste data$ and the name of the column , but this is always a 
character. 
 
When I do: is.numeric(data[257]) i get FALSE as result  
(257 is the corresponding column index to "vol")

Help needed! Thanks!
Markus




      
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Try this:

x <- data.frame(A=c(10,20), B = c("a", "b"), C =
c(20,30))
x[sapply(x, is.numeric)]

On Sat, Jul 26, 2008 at 11:19 AM, Markus M?hlbacher <muehliman at
yahoo.com> wrote:
> Hello,
>
> My question sounds simple, but as I am desperatly searchin for a solution I
am
> asking you all. :)
>
> I try to filter out all non-numeric columns of a data frame using a for
loop
> to go through all columns. My if clause looks like this:
>
>         for(j in 1:length(data)) {
>
>                 ...
>                 if(!is.numeric(data[j])) skip <- "not
numeric")
>                 ...
>         }
>
> When I do: is.numeric(data$vol) i get TRUE as result:
> unfortunately this is not applicable in a for loop, because i need to go
> through all of the columns using j.
> I also tried to paste data$ and the name of the column , but this is always
a
> character.
>
> When I do: is.numeric(data[257]) i get FALSE as result
> (257 is the corresponding column index to "vol")
>
> Help needed! Thanks!
> Markus
>
>
>
>
>
>        [[alternative HTML version deleted]]
>
>
> ______________________________________________
> R-help at r-project.org 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.
>
>


-- 
Henrique Dallazuanna
Curitiba-Paran?-Brasil
25? 25' 40" S 49? 16' 22" O