如何在r中返回具有部分子字符串匹配的逻辑向量

Question

So, what I would like to do is on a substring match one column with another column and return true if there is a partial match

A            B          C
hello      helloworld  true
worldhello hello       true
dog        hello       false

Here is a quick example of my two columns (A and B) and the logical vector I would like returned (C)

Answer 1

Calling your example df , this would do it:

sapply(1:nrow(df),function(i)with(df[i,],grepl(A,B)|grepl(B,A)))
# [1]  TRUE  TRUE FALSE

There's probably a more efficient way, though.

Answer 2

old question but for the record: you can also use dplyr to achieve this:

taking the matrix from @darwin and applying the solution from @jhoward the solution looks like this:

as.data.frame(a) %>% 
 rowwise() %>% 
 mutate(V3 = grepl(V1,V2)|grepl(V2,V1) )

you need the rowise() as grepl doesn't take a vector.

Answer 3

I think using one of the grep functions will be your best bet. And since you need to match in either column, then you will have to do it twice. I did basically the same thing as jlhoward, but mine is in a for loop.

a <- matrix(data=c("hello", "helloworld", "worldhello", "hello", "dog", "hello"), nrow=3, byrow=TRUE)
b <- rep(NA, dim(a)[1])
for(i in sequence(dim(a)[1])){
  b[i] <- sum(length(grep(a[i,1], a[i,2])), length(grep(a[i,2], a[i,1]))) > 0
}
cbind(a,b)