added regression to notebook 09

Pipfile

@@ -28,6 +28,8 @@ yapf = "*"
 pre-commit = "*"
 plotly = "*"
 watermark = "*"
+graphviz = "*"
+xgboost = "*"
 
 [dev-packages]
 

notebooks/01_introduction.ipynb

@@ -17,6 +17,8 @@
     "    * (FeatureEng): Feature Engineering for Machine Learning; Alice Zheng and Amanda Casari; O'Reilly, 2018; [Github repo](https://github.com/alicezheng/feature-engineering-book)\n",
     "    * (DSHandbook): Python Data Science Handbook; Jake VanderPlas; O'Reilly, 2016; [Github repo](https://github.com/jakevdp/PythonDataScienceHandbook)\n",
     "    * (PracticalStatistics): Practical Statistics for Data Scientists: 50+ Essential Concepts Using R and Python; Peter Bruce, Andrew Bruce, and Peter Gedeck; O'Reilly, 2nd edition, 2020; [Github repo](https://github.com/gedeck/practical-statistics-for-data-scientists/)\n",
+    "    * (PyML): Python Machine Learning;  Raschka, Sebastian, and Vahid Mirjalili; 3rd Edition, Packt Publishing, 2019; [Github repo](https://github.com/rasbt/python-machine-learning-book-3rd-edition)\n",
+    "\n",
     "    \n",
     "* Unless marked otherwise, code was written by Eva Zangerle.\n",
     "* I deliberately mix different Python packages (e.g., for visualization matplotlib, pandas and seaborn) to showcase their use.\n",