Learning D3.js 5 Mapping - Second Edition

Merging files

The final tip involves merging multiple shapefiles into a single TopoJSON file. This is extremely useful if you need separate geographic information but want to fetch it in a single Fetch request. To append additional files, you simply add them on to the command.

Consider the following commands:

First, create a new GeoJSON from the region shapefile:

   shp2json ESP_adm1.shp --out ESP_adm1.json

Then concatenate them together:

geo2topo ESP_adm1.json ESP_adm0.json > spain-regions.json

 It will take each GeoJSON file, convert them to TopoJSON, and produce the following object structure, where the data for ESP_adm0 is the data for the country, and ESP_adm1 is the data for the regions:

There is also the opportunity to rename the object ...