3.2 Java1492-plotting large quantities of data using java  (Page 24/27)

End of class plotalot03

Listing 34 signals the end of the overridden paint method, the MyCanvas class, the Page class, and the PlotALot03 class.

The class named PlotALot04

This class is an update to the class named PlotALot03 . This class is designed to plot large amounts of three-channel data on separatehorizontal axes. One set of data is plotted using the color black. The second set of data is plotted using the color red. The third set of data is plottedusing the color blue.

The class provides a main method so that the class can be run as an application to test itself.

Three steps for using the class

There are three steps involved in the use of this class for plotting data:

• Instantiate a plotting object of type PlotALot04 .
• Feed triplets of data values to the plotting object by calling the feedData method once for each triplet of data values. The first value in the triplet will be plotted in black on one axis. The secondvalue in the triplet will be plotted in red on an axis below that axis. The third value in the triplet will be plotted in blue on an axis below thatone.
• Call the plotData method on the plotting object when all of the data has been fed to the object.

A stack of page objects

The class produces a graphic output consisting of a stack of Page objects on the screen, with the data plotted on a Canvas object contained in the Page object. The page showing the earliest data is on the top of the stack and the page showing the latest data is on thebottom of the stack.

Each Page object contains three or more horizontal axes on which the data is plotted. The class will terminate if the number of axes on thepage is not evenly divisible by 3.

The three data sets are plotted on separate axes as shown in Figure 4 with the data from one data set being plotted in black on one axis, the data from thesecond data set being plotted in red on the axis below that axis, and the data from the third data set being plotted in blue on the axis below that axis.

Testing with the main method

For test purposes, the main method instantiates a single plotting object and feeds three data sets to that plotting object producing thegraphic output shown in Figure 4 .

Won't discuss the code

The code in this class is so similar to the code in the class named PlotALot03 that I'm not going to discuss the code. You will find a completelisting of the class in Listing 38 near the end of the module.

Run the programs

I encourage you to copy, compile, and run the programs that you will find in Listing 35 through Listing 38 below.

Modify the programs and experiment with them in order to learn as much as you can about the use of Java for plotting large quantities of data. For example,you might want to modify the default plotting parameters to a different set of plotting parameters that are more to your liking. One possibility is to causethe default Page size to fill the entire screen on your computer.

Another good exercise would be for you to convert this class to Swing using a look and feel that is independent of the operating system.