Separate a Link Force with optimization

src/link.js

@@ -1,100 +1,53 @@
 import constant from "./constant";
 import jiggle from "./jiggle";
-import {map} from "d3-collection";
-import {getStress} from "./stress";
 
 /**
- * Extended link force algorithm to include the stress metric for
- * comparisons between the different algorithms.
- * Everything else is the same as in D3 force module.
+ * Modified link force algorithm
+ * - ignore alpha
+ * - removed location prediction, and bias
+ * - modified strength calculation
+ * - removed other unused functions
+ * Making it more suitable for the spring model.
  */
 
-function index(d, i) {
-  return i;
-}
-
-function find(nodeById, nodeId) {
-  var node = nodeById.get(nodeId);
-  if (!node) throw new Error("missing: " + nodeId);
-  return node;
-}
-
 export default function(links) {
-  var id = index,
-      strength = defaultStrength,
-      strengths,
+  var dataSizeFactor,
       distance = constant(30),
-      distances,
+      distances = [],
       nodes,
-      count,
-      bias,
       iterations = 1;
 
   if (links == null) links = [];
 
-  function defaultStrength(link) {
-    return 1 / Math.min(count[link.source.index], count[link.target.index]);
-  }
-
-  function force(alpha) {
+  function force() {
     for (var k = 0, n = links.length; k < iterations; ++k) { // Each iteration in a tick
-      for (var i = 0, link, source, target, x, y, l, b; i < n; ++i) { //For each link
+      for (var i = 0, link, source, target, x, y, l, b; i < n; ++i) { // For each link
         link = links[i];
+        // jiggle so it wont divide / multiply by zero after this
         source = link.source;
         target = link.target;
-        x = target.x + target.vx - source.x - source.vx || jiggle();
-        y = target.y + target.vy - source.y - source.vy || jiggle();
+        x = target.x - source.x || jiggle();
+        y = target.y - source.y || jiggle();
         l = Math.sqrt(x * x + y * y);
-        l = (l - distances[i]) / l * alpha * strengths[i];
+        l = (l - distances[i]) / l  * dataSizeFactor;
         x *= l, y *= l;
-        target.vx -= x * (b = bias[i]);
-        target.vy -= y * b;
-        source.vx += x * (b = 1 - b);
-        source.vy += y * b;
+        target.vx -= x;
+        target.vy -= y;
+        source.vx += x;
+        source.vy += y;
       }
     }
   }
 
   function initialize() {
     if (!nodes) return;
-
-    var i,
-        n = nodes.length,
-        m = links.length,
-        nodeById = map(nodes, id),
-        link;
-
-    for (i = 0, count = new Array(n); i < n; ++i) {
-      count[i] = 0;
-    }
-
-    for (i = 0; i < m; ++i) {
-      link = links[i];
-      link.index = i;
-      //if (typeof link.source !== "object") link.source = find(nodeById, link.source);
-      //if (typeof link.target !== "object") link.target = find(nodeById, link.target);
-      ++count[link.source.index];
-      ++count[link.target.index];
-    }
-
-    for (i = 0, bias = new Array(m); i < m; ++i) {
-      link = links[i];
-      bias[i] = count[link.source.index] / (count[link.source.index] + count[link.target.index]);
-    }
-
-    strengths = new Array(m), initializeStrength();
-    distances = new Array(m), initializeDistance();
-  }
-
-  function initializeStrength() {
-    if (!nodes) return;
-
-    for (var i = 0, n = links.length; i < n; ++i) {
-      strengths[i] = +strength(links[i], i, links);
-    }
+    console.log("CUSTOM LINK FORCE");
+    dataSizeFactor = 0.5/(nodes.length-1);
+    initializeDistance();
   }
 
   function initializeDistance() {
+    console.log("INIT DISTANCE", links.length);
     if (!nodes) return;
 
     for (var i = 0, n = links.length; i < n; ++i) {
@@ -119,17 +72,9 @@ export default function(links) {
     return arguments.length ? (iterations = +_, force) : iterations;
   };
 
-  force.strength = function(_) {
-    return arguments.length ? (strength = typeof _ === "function" ? _ : constant(+_), initializeStrength(), force) : strength;
-  };
-
   force.distance = function(_) {
     return arguments.length ? (distance = typeof _ === "function" ? _ : constant(+_), initializeDistance(), force) : distance;
   };
 
-  force.stress = function() {
-    return getStress(nodes, function(s,t){return distance({source: s, target: t});});
-  }
-
   return force;
 }