minor edits

Author: florian-huber

notebooks/18_machine_learning_algorithms_3.ipynb

@@ -81,10 +81,10 @@
     "We here compare two possible splits (x > 3 or x > 3.5) to decide which one is better based on the Gini index. \n",
     "```\n",
     "\n",
-    "The Gini index at the root is\n",
+    "The Gini index at the beginning (in the \"parent\" node) is\n",
     "\n",
     "$$\n",
-    "Gini_{root}=1 - (0.5^2 + 0.5^2)=0.5\n",
+    "G_{parent}=1 - (0.5^2 + 0.5^2)=0.5\n",
     "$$\n",
     "\n",
     "Consider two candidate splits on feature x:\n",
@@ -101,7 +101,7 @@
     "Gini_R = 1 - (\\frac{2}{5}^2 + \\frac{8}{15}^2) ≈ 0.498\n",
     "$$\n",
     "\n",
-    "The weighted impurity after Split A is\n",
+    "The weighted sum of both $Gini_L$ and $Gini_R$ after Split A is\n",
     "\n",
     "$$\n",
     "G_A = \\tfrac{5}{20}\\times0.48 + \\tfrac{15}{20}\\times0.498 \\approx 0.493\n",