[R] lookup in R - possible to avoid loops?

Henrique Dallazuanna
2010-11-08T19:45:04Z

Try this:

 merge(my.df, my.lookup)

On Mon, Nov 8, 2010 at 5:43 PM, Dimitri Liakhovitski <
dimitri.liakhovitski@gmail.com> wrote:

> Hello!
> Hope there is a nifty way to speed up my code by avoiding loops.
> My task is simple - analogous to the vlookup formula in Excel. Here is
> how I programmed it:
>
> # My example data frame:
> set.seed(1245)
>
>
my.df<-data.frame(names=rep(letters[1:3],3),value=round(rnorm(9,mean=20,sd=5),0))
> my.df<-my.df[order(my.df$names),]
> my.df$names<-as.character(my.df$names)
> (my.df)
>
> # My example lookup table:
>
my.lookup<-data.frame(names=letters[1:3],category=c("AAA","BBB","CCC"))
> my.lookup$names<-as.character(my.lookup$names)
> my.lookup$category<-as.character(my.lookup$category)
> (my.lookup)
>
> # Just adding an extra column to my.df that contains the categories of
> the names in the column "names":
> my.df2<-my.df
> my.df2$category<-NA
> for(i in unique(my.df$names)){
>        my.df2$category[my.df2$names %in%
> i]<-my.lookup$category[my.lookup$names %in% i]
> }
> (my.df2)
>
> It does what I need, but it's way too slow - I need to run it for
> hundreds and hundreds of names in >100 of huge files (tens of
> thousands of rows in each).
> Any way to speed it up?
>
>
> Thanks a lot!
>
> --
> Dimitri Liakhovitski
> Ninah Consulting
> www.ninah.com
>
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>



--
Henrique Dallazuanna
Curitiba-Paraná-Brasil
25° 25' 40" S 49° 16' 22" O

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