[R] search and replace

Erik Iverson eriki at ccbr.umn.edu
Thu Apr 15 06:08:12 CEST 2010

Chuck wrote:
> I have a dataframe with almost a million rows which has one column
> with strings. That column has several entries with the words "South",
> "North", "East" and "West" which I would like to replace with S, N, E,
> and W, respectively. Obviously, I can use gsub multiple times   df
> $col2 <- gsub("West", "W", df$col2)  which will require multiple scans
> of the column.
> Is there a succinct approach where all the replacements can be done
> with a single scan? Thanks.

You don't give a toy example.  If they are factors, just see the ?levels 
function, including its replacement version.
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