Vega: how to include topoJSON instead of using URL in the Vega spec

Question

I use Vega charting library. Every time I switch between tabs, the app render charts and one of charts has a spec with URL of topoJSON. The spec itself is in memory, but this URL is called every time on re-rendering charts.

This example uses URL to load topoJSON of the world map: https://vega.github.io/vega/examples/zoomable-world-map/

Is it possible include topoJSON to the spec instead of using URL? Or at least cache it somehow on local (can't use CDN).

Answer 1

Here is how to supply topojson inline.

Create a data as follows

{
            "name": "i",
            "values": {},
            "format": { "type": "topojson", "mesh": "yourMesh", "filter": "exterior" }
}

Everything between the braces for values should be your entire topojson spec. yourMesh should be the feature or mesh name.

I'd post a working example but the spec it too large. You can download a PowerBI file at the following link showing this working.

https://github.com/deneb-viz/deneb/issues/194