Add entry to select between normal and tweaked Link Force

- Tweaked link force should initialize and perform the calculation a tiny bit faster (maybe insignificant)

examples/d3-force-neighbourSampling-papaparsing.html

@@ -209,8 +209,8 @@
             <input type="range" min="1" max="100" value="10" step="1" oninput="d3.select('#distanceRangeSliderOutput').text(value); SELECTED_DISTANCE=value;">
             </label>
         </div>
-        <input class="noParameters" type="radio" name="algorithm" onclick="d3.select('#startSimulation').on('click', startLinkSimulation)">Link
-        force in D3<br>
+        <input class="noParameters" type="radio" name="algorithm" onclick="d3.select('#startSimulation').on('click', startLinkSimulation); tweakedVerOfLink=false;">Link force in D3<br>
+        <input class="noParameters" type="radio" name="algorithm" onclick="d3.select('#startSimulation').on('click', startLinkSimulation); tweakedVerOfLink=true; ">Link force (tweaked)<br>
         <input class="noParameters" type="radio" name="algorithm" onclick="d3.select('#startSimulation').on('click', startBarnesHutSimulation)">Barnes-Hut<br>
         <input id="tSNEButton" type="radio" name="algorithm" onclick="d3.select('#startSimulation').on('click', starttSNE)">t-SNE<br>
         <div id="tSNEParameters" class="parameters" style="display:none">

examples/js/src/neighbourSampling-papaparsing.js

@@ -42,7 +42,8 @@ var nodes, // as in Data points
   selectedData,
   clickedIndex = -1,
   paused = false,
-  alreadyRanIterations;
+  alreadyRanIterations,
+  tweakedVerOfLink;
 
 // Default parameters
 var MULTIPLIER = 50,

examples/js/src/neighbourSampling-papaparsing/linkForce.js

@@ -32,13 +32,14 @@ function startLinkSimulation() {
    * The full pre-calculation will then occur once when the force is being
    *   initialized by the simulation.
    */
-  simulation.force(forceName,
-    d3.forceLinkOptimized()
-      .distance(function (n) {
+  let force = tweakedVerOfLink ? d3.forceLinkTweaked() : d3.forceLink();
+  force.distance(function (n) {
          return distanceFunction(n.source, n.target, props, norm);
         })
-    .links(links)
-  ).alphaDecay(0)
+       .links(links);
+  
+  simulation.force(forceName,force)
+            .alphaDecay(0)
              //.velocityDecay(0.8)
             .alpha(1)
             .restart();

index.js

@@ -13,7 +13,7 @@ export { default as forceBarnesHut}
 export { default as tSNE}
   from "./src/t-sne";
 
-export { default as forceLinkOptimized}
+export { default as forceLinkTweaked}
   from "./src/link";
 
 export { default as hybridSimulation}

src/link.js

@@ -4,10 +4,12 @@ import jiggle from "./jiggle";
 /**
  * Modified link force algorithm
  * - ignore alpha
- * - removed location prediction, and bias
+ * - removed bias
  * - modified strength calculation
  * - removed other unused functions
  * Making it more suitable for the spring model.
+ * This should initialize and perform calculation a bit faster, and also
+ * use a bit less memory
  */
 
 export default function(links) {
@@ -26,8 +28,8 @@ export default function(links) {
         // jiggle so it wont divide / multiply by zero after this
         source = link.source;
         target = link.target;
-        x = target.x - source.x || jiggle();
-        y = target.y - source.y || jiggle();
+        x = target.x + target.vx - source.x - source.vx || jiggle();
+        y = target.y + target.vy - source.y - source.vy || jiggle();
         l = Math.sqrt(x * x + y * y);
         l = (l - distances[i]) / l  * dataSizeFactor;
         x *= l, y *= l;
@@ -41,13 +43,11 @@ export default function(links) {
 
   function initialize() {
     if (!nodes) return;
-    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) {