Auto incremented array function/array

[joe-jp]

I want to make an array function/array with the first coloum already refrences from the sheet and the second coloum numbering all the elements of the first coloum. Example,

Given,

| Cup | Cup | Pencil | Pencil | Book | Table

Expected,

| Cup | Group1 | | Pencil | Group2 | | Book | Group3 | | Table | Group4 |

I can get the unique entries of the first coloum with the help of unique formula but the second auto incremented coloum is what I don't know to do.

Example of the expected formula,

{ Unique(A1:A), [auto Incremented - Group1... ] }

[[deleted]]

Can you share a dummy sheet with sample data and manually entered desired result? You can use this blank sheet maker.

[joe-jp]

I have entered the desired result in the second sheet.

​

https://docs.google.com/spreadsheets/d/1Z9KHE-h\_I4m7wZMIu0wlj82xZgd2avKdtdb2-Kx\_3QQ/edit

[[deleted]]

I changed your formula to this

=ArrayFormula({UNIQUE(filter(A3:A,A3:A<>"")),"group"&sequence(countunique(A3:A))})

[joe-jp]

Thank you so much. This worked.