diff --git a/client/src/util/centroid.js b/client/src/util/centroid.js
index bbdd021e..cc7e9d8d 100644
--- a/client/src/util/centroid.js
+++ b/client/src/util/centroid.js
@@ -4,13 +4,92 @@ import { unassignedCategoryLabel } from "../globals";
 
 /*
   Centroid coordinate calculation
+  Calculates centroids for displaying
+  In the case that a category is truncated, the truncated labels will not have
+    centroids calculated
 */
 
-/* 
-  calcMedianCentroid goes through a given metadata category
-  fetches each cell's coordinates grouping by category value.
+/*
+Generates a mapping of categorical values to data needed to calculate centroids
+categoricalValue -> {
+ length: int,
+ holdsFinite: Boolean,
+ xCoordinates: Float32Array,
+ yCoordinates: Float32Array
+}
+*/
+const getCoordinatesByCategoricalValues = (
+  obsAnnotations,
+  obsLayout,
+  categoryName,
+  layoutDimNames,
+  categoricalSelection,
+  schemaObsByName
+) => {
+  const coordsByCategoryLabel = new Map();
 
-  It then calculates the median value and puts that in the array
+  const categoryArray = obsAnnotations.col(categoryName).asArray();
+
+  const layoutXArray = obsLayout.col(layoutDimNames[0]).asArray();
+  const layoutYArray = obsLayout.col(layoutDimNames[1]).asArray();
+
+  const { categoryValueIndices, categoryValueCounts } = categoricalSelection[
+    categoryName
+  ];
+
+  // Check to see if the current category is a user created annotation
+  const isUserAnno = schemaObsByName[categoryName].writable;
+
+  // Iterate over all cells
+  for (let i = 0, len = categoryArray.length; i < len; i += 1) {
+    // Fetch the categorical value of the current cell
+    const categoryValue = categoryArray[i];
+
+    // Get the index of the categoryValue within the category
+    const categoryValueIndex = categoryValueIndices.get(categoryValue);
+
+    // If the category is truncated and this value is removed,
+    //  it will not be assigned a category value and will not be
+    //  labeled on the graph
+    // If the user created this category,
+    //  do not create a label for the `unassigned` value
+    if (
+      categoryValueIndex !== undefined &&
+      !(isUserAnno && categoryValue === unassignedCategoryLabel)
+    ) {
+      // Create/fetch the scratchpad value
+      let coords = coordsByCategoryLabel.get(categoryValue);
+      if (coords === undefined) {
+        // Get the number of cells which are in the categorical value
+        const numInCategoricalValue = categoryValueCounts[categoryValueIndex];
+        coords = {
+          hasFinite: false,
+          xCoordinates: new Float32Array(numInCategoricalValue),
+          yCoordinates: new Float32Array(numInCategoricalValue),
+          length: 0
+        };
+        coordsByCategoryLabel.set(categoryValue, coords);
+      }
+
+      coords.hasFinite =
+        coords.hasFinite ||
+        (Number.isFinite(layoutXArray[i]) && Number.isFinite(layoutYArray[i]));
+
+      const coordinatesLength = coords.length;
+
+      coords.xCoordinates[coordinatesLength] = layoutXArray[i];
+      coords.yCoordinates[coordinatesLength] = layoutYArray[i];
+
+      coords.length = coordinatesLength + 1;
+    }
+  }
+  return coordsByCategoryLabel;
+};
+
+/* 
+  calcMedianCentroid calculates the median coordinates for categorical values in a given metadata field 
+
+  categoricalValue -> [x-Coordinate, y-Coordinate]
 */
 
 const calcMedianCentroid = (
@@ -21,85 +100,39 @@ const calcMedianCentroid = (
   categoricalSelection,
   schemaObsByName
 ) => {
-  const categoryArray = obsAnnotations.col(categoryName).asArray();
+  // generate a map describing the coordinates for each value within the given category
+  const dataMap = getCoordinatesByCategoricalValues(
+    obsAnnotations,
+    obsLayout,
+    categoryName,
+    layoutDimNames,
+    categoricalSelection,
+    schemaObsByName
+  );
 
-  const layoutXArray = obsLayout.col(layoutDimNames[0]).asArray();
-  const layoutYArray = obsLayout.col(layoutDimNames[1]).asArray();
+  // categoricalValue => [medianXCoordinate, medianYCoordinate]
   const coordinates = new Map();
 
-  // Iterate over all the cells in the category
-  for (let i = 0, len = categoryArray.length; i < len; i += 1) {
-    const categoryValue = categoryArray[i];
-
-    // Get the index of the categoryValue within the category
-    // If the category is truncated and this value is removed,
-    // it will not be assigned a category value and will not be
-    // labeled on the graph
-    const categoryValueIndex = categoricalSelection[
-      categoryName
-    ].categoryValueIndices.get(categoryValue);
-
-    // Check to see if the current category is a user created annotation
-    // if the user created this category, do not create a label for the `unassigned` value
-    const isUserAnno = schemaObsByName[categoryName].writable;
-
-    if (
-      categoryValueIndex !== undefined &&
-      !(isUserAnno && categoryValue === unassignedCategoryLabel)
-    ) {
-      // Get the number of cells which are in the category value
-      const numInCategoryValue =
-        categoricalSelection[categoryName].categoryValueCounts[
-          categoryValueIndex
-        ];
-
-      // Create/fetch the valueArray,
-      // which is what the key points to in the `coordinates` hashmap
-      const valueArray = coordinates.get(categoryValue) || [
-        false, // hasFinite
-        0, // index
-        new Float32Array(numInCategoryValue), // x coordinates
-        new Float32Array(numInCategoryValue) // y coordinates
-      ];
-      const index = valueArray[1];
-      let hasFinite = valueArray[0];
-
-      hasFinite =
-        hasFinite ||
-        (Number.isFinite(layoutXArray[i]) && Number.isFinite(layoutYArray[i]));
-
-      valueArray[0] = hasFinite;
-      valueArray[1] = index + 1;
-      valueArray[2][index] = layoutXArray[i];
-      valueArray[3][index] = layoutYArray[i];
-
-      coordinates.set(categoryValue, valueArray);
-    }
-  }
-
   // Iterate over the recently created map
-  coordinates.forEach((value, key) => {
-    // If there are coordinates for this cateogrical value,
+  dataMap.forEach((value, key) => {
+    // If there are coordinates for this categorical value,
     // and there is a finite coordinate for the category value
-    if (value[2].length > 0 && value[3].length > 0 && value[0]) {
-      // Find the median x and y coordinate
-      // and insert them into the first two indices
-      value[0] = quantile([0.5], value[2])[0];
-      value[1] = quantile([0.5], value[3])[0];
-      // Remove the last two elements (where the arrays of coordinates were)
-      value.pop();
-      value.pop();
-    } else {
-      // remove the entry if not
-      coordinates.delete(key);
+    if (value.length > 0 && value.hasFinite) {
+      const calculatedCoordinates = [];
+
+      // Find and store the median x and y coordinate
+      calculatedCoordinates[0] = quantile([0.5], value.xCoordinates)[0];
+      calculatedCoordinates[1] = quantile([0.5], value.yCoordinates)[0];
+
+      coordinates.set(key, calculatedCoordinates);
     }
   });
+
   // return the map: categoricalValue -> [medianXCoordinate, medianYCoordinate]
   return coordinates;
 };
 
 // A simple function to hash the parameters
-// (not 100% on world hash, Bruce will have to check this one out)
 const hashMedianCentroid = (
   obsAnnotations,
   obsLayout,