Combine two columns into a third column as a list in R

Question

Suppose I have data frame in R

A B
d test1
e test2

Suppose I want to combine two columns A B to a new column C which is list of columns A and B

A B     C
d test1 (d,test1)
e test2 (e,test2)

Answer 1

Data:

df <- data.frame(
  A = c("d","e"),
  B = c("test1", "test2"), stringsAsFactors = F)

Solution:

apply the function paste0 to rows (1) in df, collapsing them by ,and assign the result to df$C:

df$C <- apply(df,1, paste0, collapse = ",")

Result:

df
  A     B       C
1 d test1 d,test1
2 e test2 e,test2