How to create a consecutive group number

Question

I have a data frame (all_data) in which I have a list of sites (1... to n) and their scores e.g.

  site  score
     1    10
     1    11  
              


        

Answer 1

Using the data from @Jaap, a different dplyr possibility using dense_rank() could be:

dat %>%
 mutate(ID = dense_rank(site))

   site     score ID
1     1 0.1884490  1
2     1 0.1087422  1
3     1 0.7438149  1
4     8 0.1150771  3
5     8 0.9978203  3
6     8 0.7781222  3
7     4 0.4081830  2
8     4 0.2782333  2
9     4 0.9566959  2
10    8 0.2545320  3
11    8 0.1201062  3
12    8 0.5449901  3

Or a rleid()-like dplyr approach, with the data arranged first:

dat %>%
 arrange(site) %>%
 mutate(ID = with(rle(site), rep(seq_along(lengths), lengths)))

   site     score ID
1     1 0.1884490  1
2     1 0.1087422  1
3     1 0.7438149  1
4     4 0.4081830  2
5     4 0.2782333  2
6     4 0.9566959  2
7     8 0.1150771  3
8     8 0.9978203  3
9     8 0.7781222  3
10    8 0.2545320  3
11    8 0.1201062  3
12    8 0.5449901  3

Or using duplicated() and cumsum():

df %>%
 mutate(ID = cumsum(!duplicated(site)))

The same with base R:

df$ID <- with(rle(df$site), rep(seq_along(lengths), lengths))

Or:

df$ID <- cumsum(!duplicated(df$site))