There is a miss of logic in your statement.
a - 5
b - 1
c - 1
d - 1
e - 1
f - 1
So how do you choose groups to determine 80%?
However in someway in is still possible.
IF RUNNING_SUM(SUM([Sales]) / TOTAL(SUM([Sales]))) <= 0.8
You can sort your dimension according to metric in descending order.
Example is in the attachment.
Trust this helps.
4Patrick.twbx 2.4 MB
This is called Pareto chart
• Drag Product field in columns shelf
• Drag sales measure in rows shelf
• Sort the products in descending order based on sales measure
• Now apply quick table calculations
Primary calculation type: Running total
Secondary calculation type: Percent of total
Once done then create a calculated field to highlight the products met the 80% of total sales target or you can use constant reference line like this
80% of Total Sales:
RUNNING_SUM(SUM([Sales])) / TOTAL(SUM([Sales]))>0.8
Finally you'll get something like this.
Let us know if this help. Workbook v10.5 attached for reference.
Pareto_v10.5.twbx 139.6 KB