added headings to tutorial

Author: Karmits

week_5/tutorial_week5.ipynb

@@ -564,6 +564,13 @@
     "new_data.info() # as before"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "#### x.unique(), x.value_counts(), x.sum()"
+   ]
+  },
   {
    "cell_type": "markdown",
    "metadata": {},
@@ -615,6 +622,13 @@
     "- there is 1 value each for 'No' and 'Yes'"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "#### NaNs: x.fillna(), x.dropna()"
+   ]
+  },
   {
    "cell_type": "markdown",
    "metadata": {},
@@ -697,6 +711,13 @@
     "Now let's address the 'Yes' and 'No' and the fact that the apparent integers are actually strings - all in one step."
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "#### x.map()"
+   ]
+  },
   {
    "cell_type": "markdown",
    "metadata": {},