tweak README

README.md

@@ -453,7 +453,10 @@ Tuesday | Thursday
 
 **Homework:**
 * You will be assigned to review the project drafts of two of your peers. You have until Tuesday 10/20 to provide them with feedback, according to the [peer review guidelines](project/peer_review.md).
-* **Optional:** Keep working on this competition! You can make up to 5 submissions per day, and the competition doesn't close until 6:30pm ET on Tuesday 10/27 (class 21).
+* Read [A Visual Introduction to Machine Learning](http://www.r2d3.us/visual-intro-to-machine-learning-part-1/) for a brief overview of decision trees.
+* Download and install [Graphviz](http://www.graphviz.org/), which will allow you to visualize decision trees in scikit-learn.
+    * Windows users should also add Graphviz to your path: Go to Control Panel, System, Advanced System Settings, Environment Variables. Under system variables, edit "Path" to include the path to the "bin" folder, such as: `C:\Program Files (x86)\Graphviz2.38\bin`
+* **Optional:** Keep working on our Kaggle competition! You can make up to 5 submissions per day, and the competition doesn't close until 6:30pm ET on Tuesday 10/27 (class 21).
 
 **Resources:**
 * [Specialist Knowledge Is Useless and Unhelpful](http://www.slate.com/articles/health_and_science/new_scientist/2012/12/kaggle_president_jeremy_howard_amateurs_beat_specialists_in_data_prediction.html) is a brief interview with Jeremy Howard (past president of Kaggle) in which he argues that data science skills are much more important than domain expertise for creating effective predictive models.
@@ -469,6 +472,7 @@ Tuesday | Thursday
 
 ### Class 17: Decision Trees
 * Decision trees ([notebook](notebooks/17_decision_trees.ipynb))
+* Exercise with Capital Bikeshare data ([notebook](notebooks/17_bikeshare_exercise.ipynb), [data](data/bikeshare.csv), [data dictionary](https://www.kaggle.com/c/bike-sharing-demand/data))
 
 **Homework:**
 * Read the "Wisdom of the crowds" section from MLWave's post on [Human Ensemble Learning](http://mlwave.com/human-ensemble-learning/).
@@ -480,16 +484,10 @@ Tuesday | Thursday
 * This paper, [The Science of Singing Along](http://www.doc.gold.ac.uk/~mas03dm/papers/PawleyMullensiefen_Singalong_2012.pdf), contains a neat regression tree for predicting the percentage of an audience at a music venue that will sing along to a pop song.
 * If you want to go deep into the different decision tree algorithms, this slide deck contains [A Brief History of Classification and Regression Trees](https://drive.google.com/file/d/0B-BKohKl-jUYQ3RpMEF0OGRUU3RHVGpHY203NFd3Z19Nc1ZF/view).
 
-**Installing GraphViz (optional):**
-* Mac: [Download and install PKG file](http://www.graphviz.org/Download_macos.php)
-* Windows: [Download and install MSI file](http://www.graphviz.org/Download_windows.php), and then add GraphViz to your path:
-    * Go to Control Panel, System, Advanced System Settings, Environment Variables
-    * Under system variables, edit "Path" to include the path to the "bin" folder, such as: `C:\Program Files (x86)\Graphviz2.38\bin`
-
 -----
 
 ### Class 18: Ensembling
-* Finish decision trees lesson
+* Finish decision trees lesson ([notebook](notebooks/17_decision_trees.ipynb))
 * Ensembling ([notebook](notebooks/18_ensembling.ipynb))
 
 **Resources:**