Question

I am fairly new to JSON and I want to create a choropleth example as so. http://gabrielflor.it/a-half-decade-of-rising-poverty Whenever the years are clicked it just goes to a different portion of the JSON (I’m assuming). Is this how functionality like this is usually done to avoid redrawing the whole map again and calling another JSON.js file? If so these .JSON files can get quite large?

Answer 1

Using a JSON is only a way to store values you need for each year. When you switch to another year the JS parse the JSON for the giving year and update the choropleth. For the example you have provided, here is the JSON used:

http://gabrielflor.it/static/data/saipe.json

This is a good way since you only have one JSON with every year you need and you load it only once. However since d3 needs datas this way I think you should add another JSON if you want to provide additional data like in gabrielflor example:

http://gabrielflor.it/static/js/d3.poverty-by-county.js?v=121107

He loads JSON like this with d3:

d3.json('../static/data/states.json', function (json) {
states = json;
});

or

d3.json('../static/data/saipehighlights.json', function (json) {
saipehighlights = json;
});