I have a dataframe that is sorted on one column variable high to low.

I then want to take each 20 rows, and add a column of metadata that identifies those top 20 rows. Then the next 20 rows, then the next 20 rows etc.. as groups.

Heres an example: This data frame is ordered by column B highest to lowest.

```
A <- c(1:10)
B <- c(10:1)
df <- data.frame(A, B)
print (df)
A B
1 1 10
2 2 9
3 3 8
4 4 7
5 5 6
6 6 5
7 7 4
8 8 3
9 9 2
10 10 1
```

Now I want to take each 2 rows, which would then be bins of 2 of the highest column B numbers. And I want to label each bin of 2 so it ends up like this:

```
A <- c(1:10)
B <- c(10:1)
C <- c(1,1,2,2,3,3,4,4,5,5)
df <- data.frame(A, B, C)
print (df)
A B C
1 1 10 1
2 2 9 1
3 3 8 2
4 4 7 2
5 5 6 3
6 6 5 3
7 7 4 4
8 8 3 4
9 9 2 5
10 10 1 5
```

Except that I want each bin to be 20 elements not 2 but this is the idea...

Thanks!