R separate comma separated cells into rows and Cartesian product

Question

I have mydf data frame below. I want to split any cell that contains comma separated data and put it into rows. I am looking for a data frame similar to y

Answer 1

There are times when a for loop is totally fine to work with in R. This is one of those times. Try:

library(splitstackshape)
cols <- c("name", "new")
for (i in cols) {
  mydf <- cSplit(mydf, i, ",", "long")
}

mydf
##     name AB new
##  1:   AB  A   1
##  2:   AB  A   2
##  3:   AB  A   3
##  4:   BW  A   1
##  5:   BW  A   2
##  6:   BW  A   3
##  7:    x  B   4
##  8:    x  B   5
##  9:    x  B   6
## 10:    x  B   7
## 11:    y  B   4
## 12:    y  B   5
## 13:    y  B   6
## 14:    y  B   7
## 15:    z  B   4
## 16:    z  B   5
## 17:    z  B   6
## 18:    z  B   7

---

Here's a small test using slightly bigger data:

# concat.test = sample data from "splitstackshape"
test <- do.call(rbind, replicate(5000, concat.test, FALSE))

fun1 <- function() {
  cols <- c("Likes", "Siblings")
  for (i in cols) {
    test <- cSplit(test, i, ",", "long")
  }
  test
}

fun2 <- function() {
  test %>%
    separate_rows("Likes") %>%
    separate_rows("Siblings")
}

system.time(fun1())
#   user  system elapsed 
#  3.205   0.056   3.261 
system.time(fun2())
#   user  system elapsed 
# 11.598   0.066  11.662