1st sankey attempt

forked from sticklebackspaf's block: 1st sankey attempt

<!DOCTYPE html>
<html>
<head>
    <title>Sankey.js</title>
    <meta charset="utf-8">
    <meta name="description" content="">
    <script src="https://d3js.org/d3.v5.js" charset="utf-8"></script>

  	<script src="https://cdnjs.cloudflare.com/ajax/libs/d3-sankey/0.7.1/d3-sankey.js" charset="utf-8"></script>
  
  <style>
    .path:hover {stroke-opacity: .4;
}
  </style>
  
</head>
<body>
    <svg width = "960" height = "475"></svg>
    <script>
 //attempt at replicating the energy sankey by Mike Bostock, notes are for my benifit and may not be factually correct in terms of terminology used and explanation but its my understanding at this stage.
//    select the svg defined above and pass its height and width into a constant obj
      const svg = d3.select("svg");
      const height = +svg.attr("height");
      const width = +svg.attr("width");
			const colour = d3.scaleOrdinal(d3.schemeCategory10);

// 		enter data using the v5 promise approach
      d3.json("energy.json").then(function(energy){

//    Define the sankey const, essentially saving as an object for use later. Also define the size of the sankey ("extent") to give it the parameters it must work within later on
      const sankey = d3.sankey()
      									.nodeWidth(15)
    										.nodePadding(10)
      									.extent([[1, 1], [width-10, height-10]]);;

//    create a graph instance of sankey that takes in the "energy" data
      const graph = sankey(energy);

// 		output the resultant sankey object to the console
      console.clear();

// 
//   enter data phase
//         
//   links/paths between nodes are being generated using the sankeyLinkHorizontal due
//   to using d3-sankey/0.7.1. The .link() method was changed after v0.5

//append a group to the svg object
      const link = svg.append("g") 						
      //set the group to no fill
                  .attr("fill","none") 	
      //change the colour of the links to grey
                  .attr("stroke","#000") 		
      //make the links see through
                  .attr("stroke-opacity",0.2) 
      //select all path items which creates a null set
      					.selectAll("path") 	
      //select the data to put into the null objects
              .data(graph.links) 		
      //join the data could have writtn this ".enter().append("path")"
      						.join("path")
      //give the path's a class of "path"
      								.attr("class","path") 
      
      
      //sankeyLinkHorizontal is creating all of the path information to feed the d attribute of the path svg using the data in our energy json the path appears to be situated at the mid point of the node link value minus the delta created by any other links into the same node. 
                      .attr("d",d3.sankeyLinkHorizontal()) 
      
			//setting the thickness of the paths, removing this attribute gives uniform lines
      								.attr("stroke-width", function(d) { 
                        												return Math.max(1, d.width);});
//  console.log(graph.links.source.sourceLinks);
				
        // sum the value of all nodes which are not the target of any link, therefore are at the start of the graph, and have no parents
       let sumOfNodesWithoutTarget = d3.sum(graph.nodes, function(node){
           return node.targetLinks.length == 0 ? 0 : node.value
         }) 
       
       console.log(sumOfNodesWithoutTarget)
        
       link.append("title").text(function(d){
         let proportionOfParentNode = Math.round((d.value / d.source.value) * 100) / 100
         let proportionOfNodesWithoutParent = Math.round((d.value / sumOfNodesWithoutTarget) * 100) / 100
         return d.source.name + " → " + d.target.name 
          + " \nValue: " + d.value
         	+ " \nProportion of parent: " + proportionOfParentNode
         + " \nProportion of graph: " + proportionOfNodesWithoutParent
       })

</script>
</body>

https://d3js.org/d3.v5.js

https://cdnjs.cloudflare.com/ajax/libs/d3-sankey/0.7.1/d3-sankey.js