Plotting Subsets of Data

Part 3: Create Plots for Each BY Group

To create a scatter plot for each value of a BY variable:

  1. Select Graph →Scatter Plot from the main menu.

  2. Select the latitude variable, and click Set Y. Select the longitude variable, and click Set X.

  3. Click the BY Variables tab.

  4. Scroll down in the list of variables and select the month variable. Click Add BY.

    The BY Options tab should be populated with your choices from the previous example.

  5. Click OK.

    Nine scatter plots appear, one for each month 4–12, as shown in Figure 12.13.

    Figure 12.13: Scatter Plots of Location by Month

    Scatter Plots of Location by Month


    Note that marker properties such as color, shape, and selected status are copied to each of the BY groups. In particular, the selected blue stars enable you to see the origin of each cyclone.

A few new features of the data are apparent.

  • The origin of cyclones varies with the month.

  • Cyclones early in the season (May–June) and late in the season (October–November) often originate in the Gulf of Mexico (81–98 degrees west longitude and 18–30 degrees north latitude) or in the Caribbean Sea.

  • In August and September quite a few Cape Verde cyclones are apparent. Cape Verde cyclones originate between the Cape Verde islands (23 degrees west longitude and 15 degrees north latitude) and the Lesser Antilles (60 degrees west longitude).

  • A large number of cyclones originate in the mid-Atlantic (25–35 degrees north latitude) in September, although mid-Atlantic origins are also seen in other months.

The next section describes how you can use the Workspace Explorer to view, hide, close, and compare BY-group plots.