Adding an Average Reference Line to Line Chart

[CB308]

Hi.. i have a line chart which is by time frame and want to add an "average" reference line under add-ons.

If I choose a quarter, month, year or date, the average does not change.

Want it to change based on timeframe selected.

none of the following has worked.  any help would be appreciated

Also need a median line based on the same date range selections.

=if(getselectedcount(%Date)=0, Sum (total ,<field>) / count (distinct %Date)

Sum (total <field> ) / count (distinct %date)

Avg(aggr(Sum(<field>), %Date)