Find and replace entire value in R

Question

I\'m looking for a way to use the find and replace function in R to replace the entire value of a string, rather than just the matching part of the string. I have a dataset with

Answer 1

You can use gsub as follows:

 gsub(".*experiences.*", "exp", string, perl=TRUE) 
 # As @rawr notes, set perl=TRUE for improved efficiency

This regex matches strings that have any characters 0 or more times (i.e. .*) followed by "experiences", followed by any characters 0 or more times.

In this case, you are still replacing the entire match with "exp" but by using regex, you expand the definition of the match (from "experience" to ".*experience.*") to achieve the desired substitution.

Answer 2

You can also simply use gsub() and add .* before and after the pattern like this:

string<-"TransRights"
gsub(".*sR.*","HumanRights",string)

The outcome would be

HumanRights

Answer 3

There's no need to modify the string with gsub since you know the desired value ("exp").

s = c(string,"bah","egad.experiences")

replace(s,grep("experiences",s),"exp")
# [1] "exp" "bah" "exp"

---

Speed. This is a little faster than the string modification in other@Frank's answer.

(Thanks to @rawr for pointing out that we should both turn on perl parsing.)

ss <- c(replicate(1e6,s))
system.time(replace(ss,grep("experiences",ss,perl=TRUE),"exp"))
#    user  system elapsed 
#     0.6     0.0     0.6 
system.time(gsub(".*experiences.*", "exp", ss,perl=TRUE))
#    user  system elapsed 
#    2.39    0.00    2.38

Taking away the replacement operations in each answer, it looks like the different patterns being matched make up most of the difference (contrary to what I had expected, seen in my last edit):

system.time(grep("experiences",ss,perl=TRUE))     # used in my answer
#    user  system elapsed 
#    0.64    0.00    0.64
system.time(grep(".*experiences.*",ss,perl=TRUE)) # used in purple-gravatar @Frank's answer
#    user  system elapsed 
#    1.82    0.00    1.82 

Answer 4

gsub() is used to substitute a particular string with another string. In the above code, if you do the following, your whole string changes to exp

result <- gsub(string, "exp", string)

But, if you use grep() and replace(), you will achieve your desired result.

res1 <- grep("pattern",string)

gives you all the lines with the pattern and use this in replace().

res_new <- replace(string,res1,"exp")