Car Mileage Calculator

I noticed that when you plot the data, the limits of
the graph are defined by the entire data set for all
years but when you plot just a single year the y-axis
doesn't change. i.e. I have a car we took on several
long trips in 2004, but in 2005 it only went about 30
miles/day. If you plot "all years" it shows up as
expected with a y-axis of 0 to 400. If you plot just
the 2005 year, the line is way at the bottom and
instead of a y-axis of 0 to 50 you still have 0 to 400.
The y-axis should be changed based on the data in the
data set you are interested in not on the min/max of
the entire data in the database.