expanding (exploding?) a data.frame by adding a variable containing a sequence number with dplyr

Question

I have simple data frame, let say:

dd <- data.frame(id = letters[1:4], v1 = c(0.3,0.1,0.7,1.3))
dd
  id  v1
1  a 0.3
2  b 0.1
3  c 0.7
4  d 1.3

For every row of this data frame, I want to "explode" it by adding a new variable which gives a sequence of numbers. I succeeded doing this, but it's my code is not ideal and hardly expendable:

dd %>% 
  mutate("0"=0,"5"=5,"10"=10) %>% 
  reshape2::melt(id.vars=c("id", "v1")) %>% 
  select(-variable) 
   id  v1 value
1   a 0.3     0
2   b 0.1     0
3   c 0.7     0
4   d 1.3     0
5   a 0.3     5
6   b 0.1     5
7   c 0.7     5
8   d 1.3     5
9   a 0.3    10
10  b 0.1    10
11  c 0.7    10
12  d 1.3    10

So, in this example, for every row, I add a column called value which have all three values within c(0,5,10)

This code is not ideal because the actual sequence I want is pretty much 1:70 and I don't want to write all 70 new variables in my mutate manually. There sure is a better way of doing this, can you help me?

I don't have to stay in dplyr but I want ot be able to pipe my code.

Thanks

Answer 1

library(tidyr)
dd %>% crossing(value = c(0, 5, 10))
   id  v1 value
1   a 0.3     0
2   a 0.3     5
3   a 0.3    10
4   b 0.1     0
5   b 0.1     5
6   b 0.1    10
7   c 0.7     0
8   c 0.7     5
9   c 0.7    10
10  d 1.3     0
11  d 1.3     5
12  d 1.3    10