A technique that is sometimes useful for exploring data is to show only observations that are selected. For example, suppose you are trying to understand how the wind_kts and min_pressure variables are distributed, given specific values for the latitude variable. Add the following statement at the bottom of the program window, and select Program →Run from the main menu.

   plot.ShowObs( false );

The scatter plot now displays only selected observations as shown in Figure 10.5. You can select bars in the histogram and examine how the wind speed and atmospheric pressure of storms vary as storms move from lower latitudes to higher latitudes. You can immediately see that storms at or above tend to be weaker storms without well-developed eyes.