Selecting rows with highest value within group form virtual Table

[colacan]

Hi,

Curetnly I have ID (duplicated) column only (Group column does not matter) . Starting from this column I want to create a table as below

ID	Group	Rand_Num	Max_Rand_ID
1	A	0.12	0.66
1	B	0.66	0.66
2	A	0.52	0.98
2	A	0.98	0.98
3	B	0.21	0.45
3	A	0.45	0.45
3	A	0.16	0.45

The process I tried is,
1. Generate a 'Rand_Num' column not adding a Colculated column but as DAX variable because I don’t want to increase the file size
2. Create 'Max_Rand by ID' (which is highest Rand_Num within each ID)
3. Iterate the table and filter only Rand_Num = Max_Rand_ID

I've tried it in many ways but I couldn't achieve the desired reault.

For example, 

1        EVALUATE
2        VAR Table_rand =
3            ADDCOLUMNS ( Table1, "Rand_Num", RAND () )
4        VAR Table_rand_filtered =
5            FILTER (
6                Table_rand,
7                VAR Ran_Number = [Rand_Num]
8                RETURN
9                    Ran_Number
10                        = CALCULATE (
11                            MAXX(Table_rand,[Rand_Num]),
12                            ALLEXCEPT ( Table1, Table1[ID] )
13                        )
14            )
15        RETURN
16            Table_rand_filtered

most of error happends above 10~12 rows. 

It gives either only 1 row-table with highest 'Rand_num' or it give message that can't access [Rand_Num]

It seems it can't access [Rand_Num] whenever I use Calculate()  function while I need it to calculate the highest [Rand_Num] for each ID

For me, it is too complecated using a virtual table which is always confusing. I will appretiate it if you let me know how to solve this problem. (also any articles I can study handling virtual tables)

Thanks.

[wdx223_Daniel]

@colacan 

Table_rand is a variance, when it was calculated, it is fixed, any function can change its value. so CALCULATE in your formula is invalid. it did not deploy any filter on Table_rand. MAXX alway works on the all rows of Table_rand.

[Nathaniel_C]

Hi @colacan ,
So the way the Rand() works, I was not able to use it in a measure and select that value as highest. I tried it in Power Query as well, but that did not work either.  So I created a table similiar to yours then added a Calculated Column using DAX, finally creating two measures, one that fills in every row with the highest value for each ID, and the second which fills in only if it is the highest value for that ID.

Max Rand =
VAR _curID =
    MAX ( 'rand'[ID] )
VAR _calc =
    CALCULATE (
        MAX ( 'rand'[RANDOM] ),
        FILTER ( ALLEXCEPT ( 'rand', 'rand'[ID] ), MAX ( 'rand'[ID] ) = _curID )
    )
RETURN
    _calc
=============================
Max Rand with highest value only =
VAR _curID =
    MAX ( 'rand'[ID] )
VAR _curRand =
    MAX ( 'rand'[RANDOM] )
VAR _calc =
    CALCULATE (
        MAX ( 'rand'[RANDOM] ),
        FILTER ( ALLEXCEPT ( 'rand', 'rand'[ID] ), MAX ( 'rand'[ID] ) = _curID )
    )
RETURN
    IF ( _calc = _curRand, _curRand )

Let me know if you have any questions.

If this solves your issues, please mark it as the solution, so that others can find it easily. Kudos 👍are nice too.
Nathaniel