added title
I hope this is not overkill, but I also thing it would be nice to add a title.
I like seeing complete examples so I don't have to go jumping all around different examples just to find how to do certain attributes.
@@ -13,7 +13,8 @@ line = alt.Chart(stocks).mark_line().encode(
x = 'date',
y = 'price',
color = 'symbol'
-).properties(width=800).interactive()
+).properties(width=800,
+ title="Daily closing prices with their aggregate prices").interactive()
rule = alt.Chart(stocks).mark_rule().encode(
y = alt.Y('average(price)', ),
