Initial data commit

Task/Diversity-prediction-theorem/JavaScript/diversity-prediction-theorem-2.js

@@ -0,0 +1,72 @@
+(() => {
+    'use strict';
+
+    // diversityValues :: [Num] -> {
+    //      mean-error ::  Float,
+    //     crowd-error :: Float,
+    //       diversity :: Float
+    // }
+    const diversityValues = observed =>
+        predictions => {
+            const predictionMean = mean(predictions);
+            return {
+                'mean-error': meanErrorSquared(observed)(
+                    predictions
+                ),
+                'crowd-error': Math.pow(
+                    observed - predictionMean,
+                    2
+                ),
+                'diversity': meanErrorSquared(predictionMean)(
+                    predictions
+                )
+            };
+        };
+
+    // meanErrorSquared :: Num a => a -> [a] -> b
+    const meanErrorSquared = observed =>
+        predictions => mean(
+            predictions.map(x => Math.pow(x - observed, 2))
+        );
+
+    // mean :: Num a => [a] -> b
+    const mean = xs => {
+        const lng = xs.length;
+        return lng > 0 ? (
+            xs.reduce((a, b) => a + b, 0) / lng
+        ) : undefined;
+    };
+
+
+    // ----------------------- TEST ------------------------
+    const main = () =>
+        JSON.stringify([{
+            observed: 49,
+            predictions: [48, 47, 51]
+        }, {
+            observed: 49,
+            predictions: [48, 47, 51, 42]
+        }].map(x => dictionaryAtPrecision(3)(
+            diversityValues(x.observed)(
+                x.predictions
+            )
+        )), null, 2);
+
+
+    // ---------------------- GENERIC ----------------------
+
+    // dictionaryAtPrecision :: Int -> Dict -> Dict
+    const dictionaryAtPrecision = n =>
+        // A dictionary of Float values, with
+        // all Floats adjusted to a given precision.
+        dct => Object.keys(dct).reduce(
+            (a, k) => Object.assign(
+                a, {
+                    [k]: dct[k].toPrecision(n)
+                }
+            ), {}
+        );
+
+    // MAIN ---
+    return main()
+})();