adding pandas solution as a reference to the 'means of subsets' exercise

Author: ibah

100 Numpy exercises.ipynb

@@ -1467,7 +1467,11 @@
     "D_sums = np.bincount(S, weights=D)\n",
     "D_counts = np.bincount(S)\n",
     "D_means = D_sums / D_counts\n",
-    "print(D_means)"
+    "print(D_means)\n",
+	"\n",
+    "# Pandas solution as a reference due to more intuitive code\n",
+    "import pandas as pd\n",
+    "print(pd.Series(D).groupby(S).mean())"
    ]
   },
   {

100 Numpy exercises.md

@@ -714,6 +714,10 @@ D_sums = np.bincount(S, weights=D)
 D_counts = np.bincount(S)
 D_means = D_sums / D_counts
 print(D_means)
+
+# Pandas solution as a reference due to more intuitive code
+import pandas as pd
+print(pd.Series(D).groupby(S).mean())
 ```
 
 #### 69. How to get the diagonal of a dot product? (★★★)