Re: [R] Combining series of variables using identifier

From: K. Elo <maillists_at_nic.fi>
Date: Tue, 26 Feb 2008 16:15:47 +0200

Hi,

if the columns always follow the same order (indx,var#, var#_lab ...), then You could use the column numbers and do the following:

  1. CN<-colnames(df)[#] (#=colnum of 'var#')
  2. df$NEW<-(here the expression to create the new variable)
  3. colnames(df)[ncol(df)]<-c(paste(CN,"new",sep="_"))

This can easily be built in a loop.

Hope this helps,
Kimmo

Lauri Nikkinen kirjoitti viestissään (26.02.2008):
> R users,
>
> I have df like this
>
> a <- data.frame( indx = 1:20,
> var1 = rep(c("I20", "I40", "A50", "B60"),
> each=5), var1_lab= rep(c("cat", "dog", "mouse", "horse"), each=5),
> var2 = rep(c("B20", "X40", "D50", "G60"), each=5), var2_lab=
> rep(c("car", "bicycle", "train", "bus"), each=5)) str(a)
>
> I'd like to create new variables by combining "varX" and "varX_lab"
> like this:
>
> a$var1_new <- factor(paste(a$var1, a$var1_lab, sep=": "))
> a$var2_new <- factor(paste(a$var2, a$var2_lab, sep=": "))
> a
>
> But, in the real world, I have multiple df:s and many of variables
> named by the same manner. Is there a possibility to create a function
> which combines these variables and creates new ones into the same df
> using "varX" as an identifier?
>
> Many thanks,
> Lauri
>
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