Add _.meanBy.

lodash.js

@@ -1513,7 +1513,7 @@
      * `isPlainObject`, `isRegExp`, `isSafeInteger`, `isSet`, `isString`,
      * `isUndefined`, `isTypedArray`, `isWeakMap`, `isWeakSet`, `join`, `kebabCase`,
      * `last`, `lastIndexOf`, `lowerCase`, `lowerFirst`, `lt`, `lte`, `max`,
-     * `maxBy`, `mean`, `min`, `minBy`, `noConflict`, `noop`, `now`, `pad`,
+     * `maxBy`, `mean`, `meanBy`, `min`, `minBy`, `noConflict`, `noop`, `now`, `pad`,
      * `padEnd`, `padStart`, `parseInt`, `pop`, `random`, `reduce`, `reduceRight`,
      * `repeat`, `result`, `round`, `runInContext`, `sample`, `shift`, `size`,
      * `snakeCase`, `some`, `sortedIndex`, `sortedIndexBy`, `sortedLastIndex`,
@@ -14820,7 +14820,34 @@
      * // => 5
      */
     function mean(array) {
-      return sum(array) / (array ? array.length : 0);
+      return meanBy(array, identity);
+    }
+
+    /**
+     * This method is like `_.mean` except that it accepts `iteratee` which is
+     * invoked for each element in `array` to generate the value to be averaged.
+     * The iteratee is invoked with one argument: (value).
+     *
+     * @static
+     * @memberOf _
+     * @since 4.7.0
+     * @category Math
+     * @param {Array} array The array to iterate over.
+     * @param {Function|Object|string} [iteratee=_.identity] The iteratee invoked per element.
+     * @returns {number} Returns the mean.
+     * @example
+     *
+     * var objects = [{ 'n': 4 }, { 'n': 2 }, { 'n': 8 }, { 'n': 6 }];
+     *
+     * _.meanBy(objects, function(o) { return o.n; });
+     * // => 5
+     *
+     * // The `_.property` iteratee shorthand.
+     * _.meanBy(objects, 'n');
+     * // => 5
+     */
+    function meanBy(array, iteratee) {
+      return sumBy(array, iteratee) / (array ? array.length : 0);
     }
 
     /**
@@ -15240,6 +15267,7 @@
     lodash.max = max;
     lodash.maxBy = maxBy;
     lodash.mean = mean;
+    lodash.meanBy = meanBy;
     lodash.min = min;
     lodash.minBy = minBy;
     lodash.multiply = multiply;