Assigning values to increments in a loop

[Cul33]

I have a column of data comprising blocks of 3 entries.  Each block of 3 is unique and I need to add a new column which contains n an incremental value for each of the entries within each block as A, B, C (or 1, 2, 3) then start again at the next unique block.

e.g. there could be 3 entries labelled "car" followed by another 3 entries labelled "bus". I want to assign a value of A in the new column to the first entry of car, B to the second entry, C to the third - then repeat the cycle from A for bus.

Any advice on the best way to accompish this would be greatly appreciated.

[Phil_Seamark]

HI there, Can you please post a small sample of your data so we can suggest some calculations. A mock up would be fine.

[Cul33]

Hi Phil

Thanks for the reply.  

Below is a sample (which is extracted from the preliminary stages of transformation steps, hence the data types are not applied).

Each value corresponds to a heading that I want to create, which could be A, B or C.   So for the first block of 3 entries, in rows 67 to 69 -  the first entry for period Jan 2015 to Dec 2015 I want to be able to assign a value of "A" in an adjacent column, then for the second entry  a value of "B" and the third a value of "C".  When a change in Period is identifed, i.e. in row 70, I am wanting to return a value of A again in the adjacent and then to loop through to C - which would repeat for several thousand rows

.

I hope this makes sense.

[Phil_Seamark · Accepted solution]

Hi @Cul33

In Power query, I would

1. Add an index to the core table
2. take a copy of the table.
3. group the copied table by the first three columns - adding a MIN aggregation column
4. Merge the grouped table back to the original table including the new [offset] column
5. create a NEW column that subtracts the offset from the index to generate a number that can be converted to ABC
6. remove the interum columns. 

[Cul33]

Thanks very much Phil - greatly appreciated. That addressed the issue.

If this were being done in Excel it woud lend itself well to an If function where, if the period is the same add 1 and if it changes return a value of 1 again. That would depend on the first entry having a value of 1 of course.   A nested If / VLookup / Match Index could then return the required Heading according to the value returned.  

I wonder therefore if there is a way to accompish this with DAX rather than creating a table?

[Phil_Seamark]

Do you have any other columns in your table that can help split the ties into 1,2 & 3?