在PowerBI DAX中使用RANKX

Question

I am a PowerBI newbie and I have been playing with DAX functions, more specifically, the RANKX function. Here is my data set:

+----------+-------------------------------------+-----------------+----------+
| Category |            Sub Category             |      Date       | My Value |
+----------+-------------------------------------+-----------------+----------+
| A        |              A1                     |      2018-01-01 |        2 |
| A        |              A2                     |      2018-01-02 |        4 |
| A        |              A3                     |      2018-01-03 |        6 |
| A        |              A4                     |      2018-01-04 |        6 |
| B        |              B1                     |      2018-01-05 |       21 |
| B        |              B2                     |      2018-01-06 |       22 |
| B        |              B2                     |      2018-01-07 |       23 |
| C        |              C1                     |      2018-01-08 |       35 |
| C        |              C2                     |      2018-01-09 |       35 |
| C        |              C3                     |      2018-01-10 |       35 |
+----------+-------------------------------------+-----------------+----------+

And below is my code:

Rank all rows as Column = 
    RANKX(
        'Table',
        'Table'[My Value]
        )

Unfortunately, I am getting the following error:

A single value for column 'My Value' in table 'Table' cannot be determined. This can happen when a measure formula refers to a column that contains many values without specifying an aggregation such as min, max, count, or sum to get a single result.

Any help would be greatly appreciated.

Thanks

Answer 1

Create a mesure to sum "My value" column:

Sum value = SUM(Table[My value]) 

Then use this measure to get your rank:

Rank all rows as Column = 
    RANKX(ALL(Table);[Sum value])

This will give you the rank of each sub category.

Answer 2

There is nothing wrong with your formula, you just put it in a wrong place.

There are 2 ways you can write DAX formulas in PowerBI:

• as a calculated column
• as a measure

The difference is critical, you need to learn it if you want to use PowerBI.

The formula you wrote is for calculated columns. If you create it as a measure, you will get an error. To fix the problem, go to tab "Model", click "New Column", paste your code and it should work.

If you need RANKX as a measure, Chrisoffer has given you a good answer.