Refactor: Extract getStress

src/hybridSimulation.js

@@ -1,12 +1,11 @@
-import { dispatch } from "d3-dispatch";
+import {dispatch} from "d3-dispatch";
 import constant from "./constant";
 import interpBruteForce from "./interpolation/interpBruteForce";
 import interpolationPivots from "./interpolation/interpolationPivots";
 import neighbourSamplingDistance from "./neighbourSamplingDistance";
-import { takeSampleFrom } from "./interpolation/helpers";
+import {takeSampleFrom} from "./interpolation/helpers";
 
 export default function (nodes, config) {
-
   var hybrid,
     fullSimulation,
     SAMPLE_ITERATIONS = readConf(config, "iteration", 300),
@@ -152,6 +151,6 @@ export default function (nodes, config) {
   };
 }
 
-function readConf(config, prop, default){
-  return config.hasOwnProperty(prop) ? config.prop : default,
+function readConf(config, prop, def){
+  return config.hasOwnProperty(prop) ? config.prop : def;
 }

src/interpolation/interpBruteForce.js

@@ -1,5 +1,5 @@
-import { pointOnCircle, takeSampleFrom } from "./helpers";
-import { placeNearToNearestNeighbour } from "./interpCommon";
+import {pointOnCircle, takeSampleFrom} from "./helpers";
+import {placeNearToNearestNeighbour} from "./interpCommon";
 
 export default function(sampleSet, remainderSet, distanceFn) {
   // var distance = calculateEuclideanDistance;

src/interpolation/interpCommon.js

@@ -1,4 +1,4 @@
-import { pointOnCircle, sumDistError } from "./helpers";
+import {pointOnCircle, sumDistError} from "./helpers";
 
 export function placeNearToNearestNeighbour(node, nearNeighbour, radius, sampleSubset, realDistances) {
   let

src/link.js

@@ -1,6 +1,7 @@
 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
@@ -101,27 +102,6 @@ export default function(links) {
     }
   }
 
-  /**
-    * Calculates the stress. Basically, it computes the difference between
-    * high dimensional distance and real distance. The lower the stress is,
-    * the better layout.
-    * @return {number} - stress of the layout.
-    */
-  function getStress() {
-    var m = links.length,
-      totalDiffSq = 0,
-      totalHighDistSq = 0,
-      link;
-    for (var i = 0, source, target, realDist, highDist; i < m; i++) {
-          link = links[i], source = link.source, target = link.target;
-          realDist = Math.hypot(target.x-source.x, target.y-source.y);
-          highDist = distances[i];
-          totalDiffSq += Math.pow(realDist-highDist, 2);
-          totalHighDistSq += highDist * highDist;
-    }
-    return Math.sqrt(totalDiffSq/totalHighDistSq);
-  }
-
   force.initialize = function(_) {
     nodes = _;
     initialize();
@@ -148,7 +128,7 @@ export default function(links) {
   };
 
   force.stress = function() {
-    return getStress();
+    return getStress(nodes, function(s,t){return distance({source: s, target: t});});
   }
 
   return force;

src/neighbourSamplingDistance.js

@@ -1,5 +1,6 @@
 import constant from "./constant";
 import jiggle from "./jiggle";
+import {getStress} from "./stress";
 
 /**
  * Set the node id accessor to the specified i.
@@ -216,28 +217,6 @@ export default function () {
     }
   }
 
-  /**
-    * Calculates the stress. Basically, it computes the difference between
-    * high dimensional distance and real distance. The lower the stress is,
-    * the better layout.
-    * @return {number} - stress of the layout.
-    */
-  function getStress() {
-    let totalDiffSq = 0, totalHighDistSq = 0;
-    for (let i = 0, source, target, realDist, highDist; i < nodes.length; i++) {
-      for (let j = 0; j < nodes.length; j++) {
-        if (i !== j) {
-          source = nodes[i], target = nodes[j];
-          realDist = Math.hypot(target.x - source.x, target.y - source.y);
-          highDist = +distance(source, target);
-          totalDiffSq += Math.pow(realDist - highDist, 2);
-          totalHighDistSq += highDist * highDist;
-        }
-      }
-    }
-    return Math.sqrt(totalDiffSq / totalHighDistSq);
-  }
-
   /**
    * Calculates the average velocity of the force calculation at the
    * current iteration.
@@ -280,7 +259,7 @@ export default function () {
   };
 
   force.stress = function () {
-    return getStress();
+    return getStress(nodes, distance);
   };
 
   force.velocity = function () {

src/stress.js

@@ -0,0 +1,19 @@
+/**
+  * Calculates the stress. Basically, it computes the difference between
+  * high dimensional distance and real distance. The lower the stress is,
+  * the better layout.
+  * @return {number} - stress of the layout.
+  */
+export function getStress(nodes, distance) {
+  let totalDiffSq = 0, totalHighDistSq = 0;
+  for (let j = 0; j < nodes.length; j++) {
+    for (let i = 0; i < j; i++) {
+      let source = nodes[i], target = nodes[j];
+      let lowDDist = Math.hypot(target.x - source.x, target.y - source.y);
+      let highDDist = distance(source, target);
+      totalDiffSq += Math.pow(highDDist - lowDDist, 2);
+      totalHighDistSq += highDDist * highDDist;
+    }
+  }
+  return Math.sqrt(totalDiffSq / totalHighDistSq);
+}