Creating a column with values based on order of unique values in another column

Question

Table

How to I create the number column as in the table attached, which look into the Admi_num column and check if its the first admission and then put a 1 in the number column and similarly put a 2 ,3 and so on values based on the administration_num column. Thank you

You need `data.table::rowid(PatID)` – akrun Apr 24 '21 at 17:51 — akrun, Apr 24 '21 at 17:51

score 1 · Answer 1 · answered Apr 24 '21 at 17:52

1

We can use rowid

library(data.table)
df1$Number <- rowid(df1$PatID)

answered Apr 24 '21 at 17:52

akrun

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score 1 · Answer 2 · answered Apr 24 '21 at 18:02

1

If say your data name is df, this base R way should yield similar results

ave(df$PatID, df$PatID, FUN = function(x) seq_len(length(x)))

answered Apr 24 '21 at 18:02

AnilGoyal

25,297
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another way is`with(df, ave(seq_along(PatID), PatID, FUN = seq_along))` – akrun Apr 24 '21 at 18:12
1

Thanks for the suggestion. :), next time I'll remember this instead – AnilGoyal Apr 24 '21 at 18:17

Creating a column with values based on order of unique values in another column

2 Answers2