[R] select columns from vector of column names

[MacQueen, Don]

How about

  data[ , colnames]
Or
  data[ , colnames[1]]
  data[ , colnames[2]]

-Don


On 7/9/10 11:27 AM, "Jonathan Flowers" <jonathanmflowers at gmail.com> wrote:

> Hi
> 
> I want to extract columns from a data frame using a vector with the desired
> column names.
> 
> This short example uses the select argument in the subset function to
> accomplish what I am trying to do.  Is there a better solution?
> 
> #names of desired columns
> colnames <- c("col1","col3")
> 
> #my data
> data <- data.frame("col1"=c(1,2,3),"col2"=c("A","B","C"),"col3"=c(4,5,6))
> 
> fun <- function(colname,dframe){
> nframe <- subset(dframe,select=colname)
>     vec <- nframe[,1]
>     return(vec)
> }
> 
> fun(colnames[1],data)
> fun(colnames[2],data)
> 
> [[alternative HTML version deleted]]
> 
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-- 
Don MacQueen
Environmental Protection Department
Lawrence Livermore National Laboratory
925 423-1062