CODEWITHSUNDEEP
dictionaryd3.jsgeojsontopojson
NumenorForLife
NumenorForLife

Reputation: 1746

Confusion over TopoJSON Format

I am attempting to follow mbostock's "Let's Make a Map" Tutorial here: http://bost.ocks.org/mike/map/. At a certain point in the tutorial, he writes: 

d3.json("uk.json", function(error, uk) {
    svg.append("path")
       .datum(topojson.feature(uk, uk.objects.subunits))
       .attr("d", d3.geo.path().projection(d3.geo.mercator()));
});

Without seeing the format of his topoJSON file, it is hard to determine what the equivalent "uk.objects.subunits" line is for my code (my topoJSON can be viewed here: https://gist.github.com/jcahan/e1772766f01b68b00dc9).

Would someone please help clarify how I (and future readers) can determine the inner property (eg uk.objects.subunits) of my topojson file?

Thanks for your time!

Upvotes: 0

Views: 1617

Answers (2)

cifuentes
cifuentes

Reputation: 1249

Sure.

That JSON file happens to be close friend (actually a neightboor) of the example. So you can see it atthe http://bost.ocks.org/mike/map/uk.json

Regards.

Upvotes: 1

caraka
caraka

Reputation: 106

Use the web console in your browser (I use the Firebug extension in Firefox) to view Mike's example page and you can watch the browser pull down the uk.json file and view its format. Here's the relevant snippet:

{"type":"Topology","transform":{"scale":
[0.001546403012701271,0.0010939367048704803],"translate":
[-13.69131425699993,49.90961334800009]},"objects":{"subunits":
{"type":"GeometryCollection","geometries":[{"type":"MultiPolygon","id":"ENG","arcs":[[[0]],
[[1]],[[2]],[[3]],[[4]],[[5]],[[6,7,8,9]]],"properties":{"name":"England"}},

You can see the hierarchy of uk.objects.subunits

subunits contains the GeometryCollection. Have a look at your json file and do the same.

Double check that this instruction from Mike is working:

d3.json("uk.json", function(error, uk) {
    console.log(uk);
});

Now if you peek at your JavaScript console, you should see a topology object that represents the administrative boundaries and populated places of the United Kingdom.

If you get it to work, let me know, as I cannot get my personal TopoJSON file to load, although I can get all of Mike's to do so. I've come to the conclusion that my TopoJSON file must be wrong somehow.

Upvotes: 2

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