Back propagation to find a suitable pFactor

app.js

@@ -1,5 +1,6 @@
 import { download } from "./export";
 import { render } from "./core/plot";
+import { defaultPopulationFactor } from "./core/constants"
 
 document.querySelector("#loader").classList.add("hide");
 
@@ -66,7 +67,7 @@ function load() {
       shape: cellShape,
       scale: cellScale,
     };
-    render(topoData, popData, cellDetails, year);
+    render(topoData, popData, cellDetails, year, defaultPopulationFactor);
     document.querySelector("#loader").classList.add("hide");
   });
 }

core/catogram.js

@@ -15,7 +15,7 @@ export default function () {
       return 1;
     };
 
-  function cartogram(topology, geometries, cellDetails, populationData, year) {
+  function cartogram(topology, geometries, cellDetails, populationData, year, populationFactor) {
     topology = copyTopo(topology);
     var tf = transformer(topology.transform),
       x,
@@ -61,7 +61,7 @@ export default function () {
     var values = objects.map(value),
       totalValue = sum(values);
 
-    var pFactor = populationFactor(cellDetails.scale, populationData, year);
+    var pFactor = getPopulationFactor(cellDetails.scale, populationData, year, populationFactor);
 
     if (iterations <= 0) {
       return objects;
@@ -154,18 +154,14 @@ export default function () {
     };
   }
 
-  function populationFactor(selectedScale, populationData, year) {
+  function getPopulationFactor(selectedScale, populationData, year, populationFactor) {
     switch (selectedScale) {
       case cellScale.Fixed:
         var factor =
           getTotalPopulation(populationData, 2018) /
           getTotalPopulation(populationData, year) /
-          1.6;
-        if (factor > 0.8) {
-          return factor;
-        } else {
-          return 1;
-        }
+          populationFactor;
+        return factor;
       case cellScale.Fluid:
         return 1;
     }

core/constants.js

@@ -45,3 +45,5 @@ export const cellScale = {
   Fixed: "Fixed",
   Fluid: "Fluid",
 };
+
+export const defaultPopulationFactor = 1.0

core/plot.js

@@ -11,17 +11,16 @@ import {
   dragged,
   dragended,
 } from "./events";
-import { colors, margin, width, height, strokeWidth } from "./constants";
+import { colors, margin, width, height, strokeWidth, cellScale } from "./constants";
 
 export var exportJson = {
   type: "FeatureCollection",
   features: [],
 };
 
-export function render(topo, populationData, cellDetails, year) {
+export function render(topo, populationData, cellDetails, year, populationFactor) {
   let cellRadius = cellDetails.radius;
   let cellShape = cellDetails.shape;
-  let cellScale = cellDetails.scale;
 
   let shapeDistance = getRadius(cellRadius, cellShape);
   let cols = width / shapeDistance;
@@ -56,7 +55,8 @@ export function render(topo, populationData, cellDetails, year) {
     topo,
     topo.objects.tiles.geometries,
     cellDetails,
-    populationData, year
+    populationData, year,
+    populationFactor
   ).features;
   exportFormat(topoFeatures);
 
@@ -137,7 +137,25 @@ export function render(topo, populationData, cellDetails, year) {
     }
   }
 
-  setCellSize(totalPopulation, cellCount);
+  var cellSize = getCellSize(totalPopulation, cellCount);
+
+  switch (cellDetails.scale) {
+    case cellScale.Fixed:
+      if (cellSize > 1.0) {
+        console.log(">", cellSize, populationFactor);
+        render(topo, populationData, cellDetails, year, populationFactor + 0.1);
+      } else if (cellSize < 1.0) {
+        console.log("<", cellSize, populationFactor);
+        render(topo, populationData, cellDetails, year, populationFactor - 0.1);
+      } else {
+        console.log("=", cellSize, populationFactor);
+        setCellSize(cellSize);
+      }
+      break;
+    case cellScale.Fluid:
+      setCellSize(cellSize);
+  }
+
 }
 
 function indexByCode(data) {
@@ -148,9 +166,12 @@ function indexByCode(data) {
   return obj;
 }
 
-function setCellSize(totalPopulation, cellCount) {
-  document.getElementById("cell-size").value =
-    (totalPopulation / (cellCount * 1000000)).toFixed(1) + "M";
+function setCellSize(cellSize) {
+  document.getElementById("cell-size").value = cellSize + "M";
+}
+
+function getCellSize(totalPopulation, cellCount) {
+  return (totalPopulation / (cellCount * 1000000)).toFixed(1);
 }
 
 function flattenFeatures(topoFeatures) {