set individual edge widths in Vega edge bundling - vega

Question

I'm trying to use an edge bundle but was hoping to have the edge thickness determined by the edges themselves rather than the source node they originate from.
The example given in the docs is here:
https://vega.github.io/editor/#/examples/vega/edge-bundling
The two data sources are here:
https://github.com/vega/vega-datasets/blob/master/data/flare-dependencies.json
https://github.com/vega/vega-datasets/blob/master/data/flare.json
In this example, the thickness of the edges is determined by line 170 in the script where a value of 1.5 is assigned to 'strokeWidth'.
"encode": {
"enter": {
"interpolate": {"value": "bundle"},
"strokeWidth": {"value": 1.5}
},
I had hoped to use the "size" value in the flare.json input to tailor each width separately. However, the example creates a tree from flare-dependencies.json and although the tree does pull in this value, visible in VEGA_DEBUG.view.data('dependencies') , I don't know how to access it and get those values to set each of the 'strokeWidth' elements for the edges.
Could you advise how I might do this?
Regards,

Answer 1

I was provided an answer to this as follows:
First add a formula to append the size value from the flare.json dataset as a field 'strokeWidth' by writing this at line 90 in the example:
{
"type": "formula",
"expr": datum.size/10000",
"as": "strokeWidth"
},
Next, in the marks, set the strokeWidth value for each edge in the edgebundle to the associated 'strokeWidth' in the column now created by writing this at what becomes line 176 after the above change:
"strokeWidth": {"field": "strokeWidth"}
After this, the diagram should render with edges of a thickness defined by that 'size' variable. Note that in this example, I had to scale the 'size' value in the original dataset by 10,000 to set the lines at a reasonable thickness.
In practice, I would scale the data prior to presenting it to Vega.