Chained animations/transitions over each graph node - D3.js

Question

I want to be able to change the radius of each node in my graph that i am creating using d3.js. However, i want to change the radius of each node, one at a time, and i want to able to control the delay between each change along with the sequence of the nodes.

For now this is what i have in terms of code:

var nodes = svg.selectAll(".node");
nodes.each(function() { 
  d3.select(this).
  transition().
  delay(100).
  attr("r", "5") 
});

You can replicate this simply by using the code at this link: http://bl.ocks.org/mbostock/4062045. The code that i have pasted above is simply an addition to the code at the aforementioned link.

When i run this, all the nodes in my graph transition simultaneously, i.e. grow in size (radius) simultaneously. I however want them to transition i.e. grow in size (radius), one at a time. I repeat that i want to be able to control:

1. the delay between the transition of each node and
2. the order of nodes that undergo the transitions.

Any pointers, tutorials, or even other stackoverflow answers would be great. I would ideally want some code examples.

The closest i have come to in terms of online references is this subsection of a tutorial on d3.js transitions: http://bost.ocks.org/mike/transition/#per-element. However, it lacks a concrete code example. I, being new to d3.js and javascript in general, am not able to pick it up without concrete code examples.

Answer 1

You can do this quite easily by calculating a delay based on each node's index. Mike Bostock has an example of such an implementation here. This is the relevant code:

var transition = svg.transition().duration(750),
    delay = function(d, i) { return i * 50; };

transition.selectAll(".bar")
    .delay(delay)
    .attr("x", function(d) { return x0(d.letter); }); // this would be .attr('r', ... ) in your case

To control the order of the transition, all you would then have to do is sort the array so that the elements' indices reflect the animation flow you want. To see how to sort an array, refer to the documentation on JavaScript's array.sort method and also see the Arrays > Ordering section of the D3 API reference.