Added field formula to AVG only rows with same value as current record

[noamso]

I want to add a field that shows the AVG of records in my group, for example:

AVG ( IF ( country = mycountry, salery, NULL ) )

where “country” is a field in the table, and “mycountry” is the value of “country” in this specific row.

So all the rows with “country = france” will have “countryAVG = 10”

and all the rows with “country = denmark” will have “countryAVG = 12”

What is the correct syntax to achieve that? is that even possible in a field formula?