Alternative to expand.grid for data.frames

Question

I have a data.frame df and I want that every row in this df is duplicated lengthTime times and that a new column is added that counts

Answer 1

Quick update

There is now also the crossing() function in package tidyr which can be used instead of merge, is somewhat faster, and returns a tbl_df / tibble.

data.frame(time=1:10) %>% merge(iris, by=NULL) 

data.frame(time=1:10) %>% tidyr::crossing(iris)