Grouping data and changing parts of the group

I have some duplicated data and I with to change a value of the grouped data so they are not duplicated. As you can see in the data below I have some duplicated names, therefore I wish to change the count column to 2 where we see a name for the second time. (Like further below). Im not quite sure how to so this so I tired to group my data first before changing, aggregate() looked a good function for this in base R but I couldn’t crack it

mydf
name    id   count
dave    128  1
john    123  1
steve   111  1
dave    128  1
harry   130  1
harry   130  1
will    11   1

mydf_final
name    id   count
dave    128  1
john    123  1
steve   111  1
dave    128  2
harry   130  1
harry   130  2
will    11   1

>Solution :

The row_number of data grouped by name and id is the same as the count you are looking to update.

mydf <- read.table(header = TRUE, text =
'name    id   count
dave    128  1
john    123  1
steve   111  1
dave    128  1
harry   130  1
harry   130  1
will    11   1')

library(dplyr)

mydf |>
  mutate(count = row_number(),
         .by = c(name, id))
#>    name  id count
#> 1  dave 128     1
#> 2  john 123     1
#> 3 steve 111     1
#> 4  dave 128     2
#> 5 harry 130     1
#> 6 harry 130     2
#> 7  will  11     1