[R] Problem subsetting: undefined columns

[Paul Hiemstra]

On 12/02/2011 07:20 AM, Aurélien PHILIPPOT wrote:
> Dear R-users,
> -I am new to R, and I am struggling with the following problem.
>
> -I am repeating the following  operations hundreds of times, within a loop:
> I want to subset a data frame by columns. I am interested in the columns
> names that are given by the rows of another data frame that was built in
> parallel. The solution I have so far works well as long as the elements of
> the second data frame are included in the column names of the first data
> frame but if an element from the second object is not a column name of the
> first one, then it bugs.

Hi Aurelien,

I would call this a feature, not a bug. I think R does what it should
do, you request a non-existent column and it throws an error. What kind
of behavior are you looking for instead of this error?

regards,
Paul

>
> -More concretely, I have the following data frames d and v:
> yyyymmdd<-c("19720601", "19720602", "19720605")
> sret.10006<-c(1,2,3)
> sret.10014<-c(5,9,7)
> sret.10065<-c(10,2,11)
>
>
> d<- data.frame(yyyymmdd=yyyymmdd, sret.10006=sret.10006,
> sret.10014=sret.10014, sret.10065=sret.10065)
>
> v<- data.frame(V1="sret.10006", V2="sret.10090")
> v<- sapply(v, function(x) levels(x)[x])
>
> -I want to do the following subsetting:
> sub<- subset(d, select=c(v))
>
>
> and I get the following error message:
> Error in `[.data.frame`(x, r, vars, drop = drop) :
>   undefined columns selected
>
>
>
> Any help would be very much appreciated,
>
> Best,
> Aurelien
>
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>
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-- 
Paul Hiemstra, Ph.D.
Global Climate Division
Royal Netherlands Meteorological Institute (KNMI)
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