Replacing data values based on grep result in R

Question

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.

Answer 1

您可以通过使用 grepl 和替换来对这些值的原始列进行子集化

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

Answer 2

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".