Use expand.grid on data.frame and vector

Question

df <- data.frame(x=c("a","b","c"), y = c(100,200,300))
v <- 1:4

I'm trying to add the vector v to a dataframe df such that each row of df is combined with each element of v

x   y   v
a   100 1
a   100 2
a   100 3
a   100 4
b   200 1
b   200 2
b   200 3
b   200 4
c   300 1
c   300 2
c   300 3
c   300 4

How can I achieve this result?

Answer 1

You can use crossing from the tidyr package.

tidyr::crossing(df, v)

Or if you want to do it in base R, here is one possible solution:

df2 <- df[rep(seq_len(nrow(df)), each = length(v), ]
df2$v <- rep_len(v, nrow(df2))