Creating a density heatmap
A “Density Map” is a heat map for points, not polygons. It renders a “weather style” map with smooth gradients as shown below.
Typical Density Map in QlikMaps

Set Marker Properties

A “QlikMaps for Points” or “QlikMaps for Points and Polygons” object will render points as a Density Map by simply setting the Marker Icon property to:
='Heatmap'
Weighting
By default, all points will have the same “weight,” meaning that the map will simply show the density of points in a particular geography. If you want to weight points based upon an expression, use the Marker Size expression to assign values to markers. The same expression/strategy for sizing bubbles (as detailed in Variable-Sized Bubble Plots) can be used here.