Optimize subset randomizer for interp

src/interpolation/helpers.js

@@ -10,12 +10,19 @@
  */
 export function takeSampleFrom(sourceList, amount) {
   let randElements = [],
-      max = sourceList.length;
+      max = sourceList.length,
+      swap = false;
 
   if (amount >= max) {
     return {sample: sourceList, remainder: {}};
   }
 
+  // If picking more than half of the entire set, random to pick the remainder instead
+  if (amount > Math.ceil(max/2)){
+    amount = max - amount;
+    swap = true;
+  }
+
   for (let i = 0; i < amount; ++i) {
     let rand = sourceList[Math.floor((Math.random() * max))];
     // Re-random until suitable value is found.
@@ -28,11 +35,19 @@ export function takeSampleFrom(sourceList, amount) {
     return !randElements.includes(obj);
   });
 
+  if(swap) {
+    return {
+      sample: remainder,
+      remainder: randElements
+    };
+  }
+  else {
     return {
       sample: randElements,
       remainder: remainder
     };
   }
+}
 
 /**
  * With a circle radius r, and center at (h,k),