Suppose I have the dataset
|ID |
| 1 | | 1 | | 1 | | 1 | | 2 | | 2 | | 2 |
I want to create a new variable where I add all the rows with the same ID number. It should look like
| ID | New |
|---|---|
| 1 | 4 |
| 1 | 4 |
| 1 | 4 |
| 1 | 4 |
| 2 | 3 |
| 2 | 3 |
| 2 | 3 |
Because I have four 1s, and three 2s.
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1With `dplyr` you could use `add_count(ID)`. – Seth Jun 26 '23 at 12:47
1 Answers
1
df %>% summarise(n = n(), .by = ID)
ID n
1 1 4
2 2 3
# or, if you want duplicates:
df %>% mutate(n = n(), .by = ID)
ID n
1 1 4
2 1 4
3 1 4
4 1 4
5 2 3
6 2 3
7 2 3
Mark
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1`df <- data.frame(ID=c(rep(1,4), rep(2,3))) %>% group_by(ID) %>% mutate(new=n())` – jkatam Jun 26 '23 at 12:57