I have plot states map using D3 and I am able to plot Centroid of each state using path.Centroid() function but once I merge the states(polygons) to make it large region path.Centroid() does not work.
How to find Centroid of merged Ploygons ?
Reference: here is the link to merged states example
Note: I have list of lat/long for all states centroid.
To find the centroid on the 'Merging States' example:
var mergeTopo = topojson.merge(us, us.objects.states.geometries.filter(function(d) { return selected.has(d.id); }));
var mergeCentroid = [path.centroid(mergeTopo)];
svg.selectAll(".mergedcentroid").data(mergeCentroid)
.enter().append("circle")
.attr("class", "mergedcentroid")
.attr("fill", "black")
.attr("stroke", "purple")
.attr("stroke-width", 5)
.attr("r", 15)
.attr("cx", function (d){ return d[0]; })
.attr("cy", function (d){ return d[1]; });
Wrapping the centroid coordinates in an array before creating the circle.