How to attach properties other than x,y,y0 to a layer of streamgraph in d3?

d3.js, javascript, json, stream-graph

Solution

Use stack.values, and then wrap each layer's data points with some additional data for the layer. Your data will look something like this:

[
  {
    "type": "apples",
    "values": [
      { "x": 0, "y":  91},
      { "x": 1, "y": 290}
    ]
  },
  {  
    "type": "oranges",
    "values": [
      { "x": 0, "y":  9},
      { "x": 1, "y": 49}
    ]
  }
]

And the stack layout like this:

var stack = d3.layout.stack()
    .offset("wiggle")
    .values(function(d) { return d.values; });

Problem

I am a d3 newbie and I've been trying to customize the Streamgraph example (http://mbostock.github.com/d3/ex/stream.html): I have run into some issues: I want to assign a custom data property (for examples sake, lets just say its a label called "type") to each layer in the stream so that when you hover over that layer, a popup box appears with the "type" listed for that layer. When I input my data source into the graph I use this code: ``` vis.selectAll("path") .data(data0) .enter().append("path") ``` The graph only seems to take data of the format: ``` [ [ { "x": 0, "y": 91, "y0": 1.11 }, { "x": 1, "y": 290, "y0": 1.11 } ], [ { "x": 0, "y": 9, "y0": 1.11 }, { "x": 1, "y": 49, "y0": 1.11 } ] ] ``` Where each sub-array above corresponds to a layer in the streamgraph. How can I pass data to the graph that allows me to add an extra "type" property for each layer? Basically so that when I refer to the datum of a layer, I can just type something like d.type and extract that property? I originally came up with a really hackish way to do it: ``` [ { "x": 0, "y": 9, "y0": 1.11, "type": "listings" }, { "x": 1, "y": 49, "y0": 1.11, } ] ``` and then I refer to it in the layer datum by saying d[0].type, but this doesn't seem like the proper way to do it.

Original source