1. Select "Change Style"
2. Select the "Choose an attribute to show" drop-down menu, scroll to the bottom of the list, and select "New Expression"
3. Enter the following under "Expression" on line 1:
4. Select "OK"
5. Select "Counts and Amounts (Color)" as your drawing style.
That should get you the heat map you are looking for.
Thanks for the reply!
I think you are talking about desktop or online version?
But I need to use the JS API to render a web map on the fly. So the sum and display needs to be dynamically done.