Custom dimension rollup to achieve average balance of balances

In the article "using calculated members to achieve the daily average", we achieved the average of the balance by establishing a calculation member, so as to guarantee the dimension of the bus structure! The disadvantage of this method, of course, is that many computational members need to be set up, and the efficiency of the calculated members is poor.
In this section, we use the custom rollup method of the dimension to achieve the average balance.
The advantage is: high efficiency (aggregation has been saved), the disadvantage is that the dimension is private, only for the balance of the cube;

Suppose the date dimension hierarchy is: Year, quarter, month, and day, the amount is "fund balance", and the granularity of the data is "Day"; the dimension name is: date;
1: Subordinate member average
such as: average annual average = year of each quarter, monthly average = month daily mean;
We can use the following custom rollup formula in the year, quarter, month, and other levels of custom Rollup formula:
AVG ([Date].currentmember.children)
2: Daily average
Whether annual, quarterly or monthly averages are the average for all the following days;
You can use the following custom rollup formula at the year, Quarter, month, and other levels of custom Rollup formula:
AVG (Descendants ([date].currentmember,4-[date].currentmember.level.ordinal)