CODEWITHSUNDEEP
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user1754606
user1754606

Reputation: 1379

Replacing data values based on grep result in R

I have a data frame. One of the columns has values like:

WIND
WINDS
HIGH WIND
etc

among the other values. Now I want to rename every value that has some variation of "WIND" in it, with "WIND". I know how to find values that I need to replace:

grep("WIND", df$col1)

but not how to replace those values. Thanks.

Upvotes: 5

Views: 10685

Answers (2)

Steve Reno
Steve Reno

Reputation: 1384

You can just subset the original column for these values by using grepl and replace

df$col1[grepl("WIND",df$col1)]<-"WIND"

Upvotes: 7

BrodieG
BrodieG

Reputation: 52637

UPDATE: a bit of a brainfart, agrep actually doesn't add anything here over grep, but you can just replace the agrep with grep. It does if you have some words that have roots that vary slightly but you still want to match.

Here is an approach using agrep:

> wind.vec
[1] "WINDS"      "HIGH WIND"  "WINDY"      "VERY WINDY"
> wind.vec[agrep("WIND", wind.vec)] <- "WIND"
> wind.vec
[1] "WIND" "WIND" "WIND" "WIND"

The nice thing about agrep is it matches approximately, so "WINDY" is replaced. Note I'm doing this with a vector, but you can easily extend to a data frame by replacing wind.vec with my.data.frame$my.wind.col.

agrep returns the indices that match approximately, which then allows me to use the [<- replacement operator to replace the approximately matching values with "WIND".

Upvotes: 1

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