A small plugin for apps that draw static or dynamic (moving) graphs, and specifically for apps that use d3.js, that makes it possible to draw several straight, parallel links between any two nodes in the graph
If you use NPM, npm install d3-parallel-links. Otherwise, download the latest release.
d3.parallelLinksInitLinks(links, LINK_WIDTH = 2)
Calling this method is a necessary init step. The first parameter is the links array of your graph data. The second, optional parameter, informs parallel-links about how your style your link widths in pixels. parallel-links uses it to set the spacing between each two adjacent parallel links.
d3.parallelLinksTransform(linkDatum)
This method does the actual drawing of the parallel links, by computing a css transform that will translate the given link in the appropriate direction and distance. It can be used in the following way, with standard d3 selections:
link
.attr('x1', function (d) {
return d.source.x;
})
.attr('y1', function (d) {
return d.source.y;
})
.attr('x2', function (d) {
return d.target.x;
})
.attr('y2', function (d) {
return d.target.y;
})
.attr('stroke', function (d) {
return d.color;
})
.attr('transform', d3.parallelLinksTransform)
d3.parallelLinksSetMethodExact(on: boolean)
d3.parallelLinksSetMethodApprox()
d3.parallelLinksIsMethodExact(): boolean
Optional: parallel-link has two alternative mode of computation. In the exact mode (which is the default), it uses trigonometric and inverse trigonometric functions. In the approximate mode, it uses only arithmetic operators. This may yield better performance. You can use the above three methods to switch between modes, and/or get the current mode.
if you are interested in more details on the mathematics, see here