From 37058ce63058cc2d5108d028a00fe82e455e5eab Mon Sep 17 00:00:00 2001
From: hadley <h.wickham@gmail.com>
Date: Fri, 22 Jul 2016 11:16:50 -0500
Subject: [PATCH] Cancelled flights exercise

Fixes #117
---
 transform.Rmd | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/transform.Rmd b/transform.Rmd
index ce142ee..3193d91 100644
--- a/transform.Rmd
+++ b/transform.Rmd
@@ -813,6 +813,9 @@ daily %>%
     
     Which is more important: arrival delay or departure delay?
 
+1.  Our definition of cancelled flights (`!is.na(dep_delay) & !is.na(arr_delay)`
+    ) is slightly sup-optimal. Why? Which is the most important column?
+
 1.  Look at the number of cancelled flights per day. Is there a pattern?
     Is the proportion of cancelled flights related to the average delay?