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

We can use the separate_rows function from the tidyr package.

library(tidyr)

mydf2 <- mydf %>%
  separate_rows("name") %>%
  separate_rows("new")
mydf2

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

If you don't what to use separate_rows function more than once, we can further design a function to iteratively apply the separate_rows function.

expand_fun <- function(df, vars){
  while (length(vars) > 0){
    df <- df %>% separate_rows(vars[1])
    vars <- vars[-1]
  }
  return(df)
}

The expand_fun takes two arguments. The first argument, df, is the original data frame. The second argument, vars, is a character string with the columns names we want to expand. Here is an example using the function.

mydf3 <- expand_fun(mydf, vars = c("name", "new"))
mydf3
#    AB name new
# 1   A   AB   1
# 2   A   AB   2
# 3   A   AB   3
# 4   A   BW   1
# 5   A   BW   2
# 6   A   BW   3
# 7   B    x   4
# 8   B    x   5
# 9   B    x   6
# 10  B    x   7
# 11  B    y   4
# 12  B    y   5
# 13  B    y   6
# 14  B    y   7
# 15  B    z   4
# 16  B    z   5
# 17  B    z   6
# 18  B    z   7