I'm using the Leaflet.js library to generate a choropleth map of zip codes colored by some property values stored within an externally loaded GeoJSON file. I'm following a tutorial [here][1] but have run into some trouble, since the tutorial shows how to access the data through assigning it to a variable within the code. I'd like to proceed without explicitly assigning a variable (i.e. using the AJAX function I currently have in place to load the data).

I've been able to display the raw data (viewable [here][2], source code available upon "View Source" in your browser) on the map, but have been unsuccessful in displaying the properties I'm interested in showing. I suspect I need to add some lines within the function that is loading the data, but can't understand how to do that.

  [1]: http://leafletjs.com/examples/choropleth.html
  [2]: http://www.unc.edu/~shafferk/catl_interface/choro.html