4

Programming JClass Chart 3D:
Scatter Plots

Overview  Three Basic Types of Scatter Plots 

Controlling Symbol and Drop Line Style  Chart Styles

All elements mentioned in this chapter refer to both the Java 2 API and the Java 3D API, unless specifically noted.

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4.1 Overview

As noted in the previous chapter, if grid data is provided to the chart via the elevationDataSource property of the Chart3dDataView class, then surface, bar, or scatter plots can be drawn. The previous chapter dealt with surface charts and bar charts; this chapter deals with scatter plots.

A scatter plot can be drawn using grid data, but the most usual way of providing data to a scatter plot is to provide the elevationDataSource with point data. This type of data supports an arbitrary number of series, each containing an arbitrary number of points.

An object can be a point data source if it implements the Chart3dPointDataModel. When a point data source is passed to a Chart3dDataView object, the data is extracted and stored in an internal point data object of type Chart3DPointData. This object can be retrieved via the elevationData property of Chart3dDataView.

More sophisticated point data sources can implement the LabelledChart3dPointDataModel, EditableChart3dDataModel, HoleValueChart3dDataModel, and the Chart3dDataManager interfaces.

Please see Data Sources, in Chapter 5, for further details.

Each series can have a symbol that makes it distinct from that of the other series. When a chart of type SCATTER is used in conjunction with grid data, each grid point will define a point in the scatter plot.

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4.2 Three Basic Types of Scatter Plots

JClass Chart 3D offers three basic types of scatter plots: 3D scatter plots, 3D scatter plots with drop lines, and 2D scatter plots. (3D scatter plots with drop lines are not currently available in the Java 3D API version of JClass Chart 3D.)

Figure 20 :  Scatter Plot examples.

Drop lines are lines drawn from each point on the 3D scatter plot down to the matching (x,y) position on the Z-axis origin of the plot cube. The drop line joins the point (x, y, z) to the matching point (x, y, origin). Drop lines are not used for 2D scatter plots. To draw drop lines on 3D scatter plots, set the dropLines property of the JCScatter class to true.

2D scatter plots use only the X- and Y-values, and ignore the z components. They are "flat" charts. These plots are created by setting both the meshed and the shaded properties of the JCElevation object to false.

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4.3 Controlling Symbol and Drop Line Style

4.3.1 Point Data

The style of symbols and drop lines used in scatter plots is determined on a per series basis. The chartStyle property of the Chart3dPointSeries specifies the line and symbol style information for a series.

A list of Chart3dPointSeries objects can be obtained from the series property of the internal point data object. This object, of type Chart3dPointData, can be retrieved via the data view's elevationData property.

Here is a code sample that changes the line style of the third series of a scatter plot. This code sample assumes that a point data source has already been set on the data view.

Chart3dPointData pointData=(Chart3dPointData)dataView.getElevationData();
ArrayList series=pointData.getSeries();
Chart3dPointSeries pointSeries=(Chart3dPointSeries)series.get(2);
JCChartStyle chartStyle=pointSeries.getChartStyle();
chartStyle.setLineStyle(new JCLineStyle(2, color.blue, JCLineStyle.SOLID));

Line pattern, color, and width are controlled by the chart style's LineStyle property, and symbol color, size, and pattern by the chart style's SymbolStyle property.

4.3.2 Grid Data

If either the zoned or contoured properties of JCContour are true, the symbol color and style, along with the dropline style, will be chosen through the appropriate contourStyle for the contour level to which the point belongs.

Note: This makes use of the JCContourStyle class' lineStyle and symbolStyle properties.

If both zoned and contoured are false, the symbol color and style, along with the dropline style, will be chosen through the chartStyle property if the internal Chart3dGridData object is associated with the grid data.

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4.4 Chart Styles

In a scatter plot, how a data value looks when it is displayed (for instance, color, line pattern, symbol style, line thickness, and so forth) depends on the chart style that has been defined for that data value. For example, the values in the third series of data will be rendered on screen using the chart style associated with the third series of the point data.

4.4.1 Default Chart Styles

When a new Chart3dPointSeries object is created, a default chartStyle is created that possesses default line and symbol styles. The defaults are cycled, so consecutive calls will return different chart styles. A user may choose to override these defaults.

The JCChartStyle class has two main components: a JCSymbolStyle object that stores symbol information and a JCLineStyle object that stores line style information. For convenience, the user can either set or get the symbolStyle or lineStyle properties of the JCChartStyle class, or the user can set the individual symbolStyle or lineStyle properties directly on the chartStyle.

For example, the following line of code:

chartStyle.setLineWidth(2);

will change the line width of the chartStyle's lineStyle object.

The JCChart3dStyle data structure contains all the information about how a set of data will be represented graphically. The properties are broken down as follows:

symbol color	The color used when drawing symbols.
symbol size	The size is the diameter in pixels of the scatter symbol. It must be greater than or equal to 1.
symbol shape	The shape of the symbol. For example, JCSymbolStyle.DOT. Available shapes are dot, box, triangle, diamond, star, vertical line, horizontal line, cross, circle, square, and rectangle for the Java 2 API version of JClass Chart 3D, and sphere, cube, cone, point, cylinder, and tetrahedron for the Java 3D API version of JClass Chart 3D.
line pattern	The line pattern used for drop lines. Available line patterns are none, solid, long dash, short dash, long-short-long dash, and dash-dot. Default is solid. Custom patterns are also possible.
line color	The color used when drawing drop lines.
line width	The line width used for drop lines. Must be greater than or equal to 1.

The following method will print out the symbol size being used for the series of data, and double it:

public void double SymbolSize (Chart3dDataView dataView, int seriesIndex)
{
  Chart3dPointData pointData=(Chart3dPointData)dataView. getElevationData();
  ArrayList series=pointData.getSeries();
  Chart3dPointSeries pointSeries=(Chart3dPointSeries)series(seriesIndex);
  JCChartStyle chartStyle=pointSeries.getChartStyle();
  system.out.println("symbol size:"+chartStyle.getSymbolSize());
  chartStyle.setSymbolStyle(2*chartStyle.getSymbolSize());
}

4.4.2 Grid Data

For grid data, the JCSymbolStyle object and the JCLineStyle object that determine how each point is drawn are obtained from either a JCContourStyle object or a JCChartStyle object. See Grid Data, in Chapter 4, for more information.