Find rows where one column string is in another column using dplyr in R

Question

Looking to pull back rows where the value in one column exists as a string in another column (within the same row).

I have a df:

A <- c("cat", "dog", "boy")
B <- c("cat in the cradle", "meet the parents", "boy mmets world")

df <- as.data.frame(A, B)

A       B
cat     cat in the cradle
dog     meet the parents
boy     boy meets world

I'm trying things like:

df2 <- df %>%
          filter(grepl(A, B)) # doesn't work because it thinks A is the whole column vector

df2 <- df %>%
          filter(B %in% A) # which doesn't work because it has to be exact

I want it to produce

A       B
cat     cat in the cradle
boy     boy meets world

Thanks in advance!

Matt

Answer 1

You can either apply the function to both vectors using Map or iterate through the row using sapply

df %>%
  filter(unlist(Map(function(x, y) grepl(x, y), A, B)))
    A                 B
1 cat cat in the cradle
2 boy   boy mmets world

df %>%
  filter(sapply(1:nrow(.), function(i) grepl(A[i], B[i])))
    A                 B
1 cat cat in the cradle
2 boy   boy mmets world