map: data being visualized

[MrichardsPSRC]

When I created a map, it appears that it's showing the median household income:

However, when I uncheck the 'Population' layer, the color disappears? the layer that is providing the data for visualization is tied to the 'Population' layer?

It might be good to include an argumnet in the function asking for the field from which to draw the numeric data? Right now it asks for the table and the spatial layer, but doesn't ask for the field being mapped?

In the table I'm providing, I would like to map the 'estimate' field