Review Heat Map code and functions used

[eric-fegraus]

Make sure IDW makes sense in this case

[pavlovc2]

We discussed several options for the heat map at the data dive. In my mind, IDW made sense because you don't really have any information about what's happening between the points. Any sort of density calculation (like this example) implies that there are fewer occurrences between monitor locations or at the edge of the study area, which seems misleading to me. You could do something fancier like kriging, but I'm not sure that will add much to the results. Habitat suitability analyses based on additional data layers are another option, but I think that could be a real headache for several reasons. But you probably know more about the end goal, so perhaps you have a different perspective.