Setting to NULL works only if a single column is selected.
More generally,
df[, !(colnames(df) %in% c("var.b", "var.c")), drop=FALSE]
-Christos
> -----Original Message-----
> From: r-help-boun...@r-project.org
> [mailto:r-help-boun...@r-project.org] On Behalf Of Sean Zhang
> Sent: Tuesday, February 24, 2009 3:10 PM
> To: r-help@r-project.org
> Subject: [R] how to NULL multiple variables of a df efficiently?
>
> Dear R-helpers:
>
> I am an R novice and would appreciate answer to the following
> question.
>
> Want to delete many variables in a dataframe.
> Am able to delete one variable by assigning it as NULL Have a
> large number of variables and would like to delete them
> without using a for loop.
>
> Is there a command/function which does this job?
>
> Many thanks in advance.
>
> -Sean
>
>
> #Small Example:
>
> df<-data.frame(var.a=rnorm(10), var.b=rnorm(10),var.c=rnorm(10))
> df[,'var.a']<-NULL #this works for one single variable
> df[,c('var.a','var.b')]<-NULL #does not work for multiple variables
>
> [[alternative HTML version deleted]]
>
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>
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