Individual "tiles" can represent several rows of the data table (geographic region: data of many countries). Then the values of the rows are averaged automatically. This is very convenient
- but "averaging" (mean) is just one option ...
If the user wants to do different aggregations, he has to generate a summary table or use a formula column with exactly the same grouping settings as the desired heat map:
Can't user already do this by using Color property and by changing summary statistic in that? If no color column is defined heatmap will use Count (that is really only thing it can use without "third axis"?).