Using a field-selection parameter in functions

Hi ant_lah 

The issue you're facing is that field parameters are not actual columns but references to columns. They act as dynamic links rather than holding values themselves.

Because of this, they are great for filtering or displaying data as a dimension in visuals, but they cannot be used directly inside aggregation functions like SUM().

Instead of using a field parameter to reference a column for aggregation, create separate measures for each calculation and use a parameter to switch between the measures instead of switching between columns.

For example, instead of SUM(Par_farms_select_1[Par_farms_select_1]), which doesn't work because Par_farms_select_1 is a reference, you should define separate measures like this:

Total_Number = SUM('C_Farms'[number total]),

Total_Area = SUM('C_Farms'[area total]),

Total_Owned = SUM('C_Farms'[number owned]).

Then, create a new field parameter that switches between these measures, just as you would with columns. Instead of selecting columns when defining the parameter,  drag the measures into the parameter setup