Re: [R] Remove non-numerical columns from data frame

From: Peter Dalgaard <p.dalgaard_at_biostat.ku.dk>
Date: Sat, 26 Jul 2008 18:35:22 +0200

Henrique Dallazuanna wrote:
> Try this:
>
> x <- data.frame(A=c(10,20), B = c("a", "b"), C = c(20,30))
> x[sapply(x, is.numeric)]
>
>
Yes, and read ?Extract to clear up the confusion between data$vol and data[257] and data[[257]] (Section on "Recursive (list-like) objects:"). Also, ?Extract.data.frame.

> On Sat, Jul 26, 2008 at 11:19 AM, Markus Mühlbacher <muehliman@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")
>>
>

-- 
   O__  ---- Peter Dalgaard             Ĝster Farimagsgade 5, Entr.B
  c/ /'_ --- Dept. of Biostatistics     PO Box 2099, 1014 Cph. K
 (*) \(*) -- University of Copenhagen   Denmark      Ph:  (+45) 35327918
~~~~~~~~~~ - (p.dalgaard_at_biostat.ku.dk)              FAX: (+45) 35327907

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