Replace a common string across two columns with a string from a different column in a dataframe in R

Question

Suppose we have a data frame as below :

test<-data.frame(v1=c(1:10),v2=c(rep("a x",10)),v3=c(rep(c("a b","a c","a d","a e","a f"),2)),v4=c((rep("p",5)),rep("q",5)))

Basically, we need to replace "a" in the strings of columns 2 and 3 with the string mentioned in column 4. The result data frame should ideally look like this:

result<-data.frame(v1=c(1:10),v2=c(rep("p x",5),rep("q x",5)),v3=c("p b","p c","p d","p e","p f","q b","q c","q d","q e","q f"),v4=c((rep("p",5)),rep("q",5)))

Have tried the following to get the same:

for (i in 1:nrow(test))
{
test[i,2]<-gsub("a",test[i,4],test[,2])
test[i,3]<-gsub("a",test[i,4],test[,3])
}

Have also tried using apply functions, but wasn't able to achieve the desired result.

Any help in this regard would be highly appreciated. Thanks in advance!

akrun · Accepted Answer · 2016-06-30 11:58:34Z

1

We can loop over the columns, remove the 'a' and paste with the 'v4'

test[2:3] <- lapply(test[2:3], function(x) paste0(test$v4, sub("a", "", x)))

answered Jun 30, 2016 at 11:58

akrun

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gowerc · Accepted Answer · 2016-06-30 11:47:19Z

1

Perhaps this? (not sure how generic you need the code to be)

test2 <- test
test2$v2 <- mapply(gsub ,  "a" , test$v4 , test$v2)
test2$v3 <- mapply(gsub ,  "a" , test$v4 , test$v3)

answered Jun 30, 2016 at 11:47

gowerc

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