Database Reference
In-Depth Information
Figure 9-5. Updated line chart with added reference line
The Dual-Axis Line Chart
What else changed in 1981 that could give us a clue as to the reason for the reversal in the
strikeout trend? The data set also includes a field called
#Pitch
, representing the total num-
ber of pitchers that played in each season. It also includes the number of teams in the league
each year in a field called
Tms
. We can create a simple ratio by dividing the total number of
pitchers by the total number of teams each year, resuling in
Pitchers per Team
.
Let's see how the number of pitchers used by teams changed over the course of the same
period of time. If we drag the
Pitchers per Team
Measure onto the Rows shelf next to
strikeouts, we create a second line chart below the first, as shown in
Figure 9-6
,
with the
trend line for the new time chart added.
