Minor updates

Author: jdfoote

day_7/day_7.ipynb

@@ -4,7 +4,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "## Introduction to Plotting with Seaborn\n",
+    "# Introduction to Plotting with Seaborn\n",
     "\n",
     "Much of today's lecture will be taken from the really wonderful [tutorial on Seaborn](https://seaborn.pydata.org/tutorial).\n",
     "\n",
@@ -800,6 +800,22 @@
     "           data=tips);"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Matplotlib\n",
+    "\n",
+    "One final note is that `seaborn` is built on top of `matplotlib` and is designed to make plotting easier. Once in a while, you may find that there's something you can't do easily in `seaborn` and you need to use `matplotlib` directly. It's beyond the scope of this class, but [here are some examples of cool plots using matplotlib](https://matplotlib.org/3.2.1/tutorials/introductory/sample_plots.html#sphx-glr-tutorials-introductory-sample-plots-py)."
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Exercises"
+   ]
+  },
   {
    "cell_type": "markdown",
    "metadata": {},