Create new variable that counts number of repeated values

Question

My dataset is such:

structure(list(NUMERO = structure(c(1, 2, 3, 3, 4, 5, 6, 6, 6, 
    6), format.stata = "%12.0g"), sexe = structure(c(1L, 1L, 2L, 
    1L, 2L, 1L, 2L, 1L, 2L, 1L), levels = c("Dona", "Home"), class = "factor"), 
        edat = c(71, 73, 44, 44, 70, 69, 56, 56, 23, 19)), row.names = c(NA, 
    -10L), class = c("tbl_df", "tbl", "data.frame"))

numero is my id variable, and I want to create a new variable that counts how many values in numero are repeated and assign the sum to each observation. So, if there are 4 observations whith numero = 6, then for this observations membres should be 4.

In other words, this is the output I'm looking for:

Answer 1

Either do add_count

library(dplyr)
df1 %>%
  add_count(NUMERO, name = "membres")

---

or use

library(dplyr) # version >= 1.1.0
df1 %>% 
   mutate(membres = n(), .by = NUMERO)

-output

# A tibble: 10 × 4
   NUMERO sexe   edat membres
    <dbl> <fct> <dbl>   <int>
 1      1 Dona     71       1
 2      2 Dona     73       1
 3      3 Home     44       2
 4      3 Dona     44       2
 5      4 Home     70       1
 6      5 Dona     69       1
 7      6 Home     56       4
 8      6 Dona     56       4
 9      6 Home     23       4
10      6 Dona     19       4