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Chart Basics

Successful charting requires that you become familiar with basic chart processes and vocabulary. The following topics cover basic information that anyone who intends to create 2D charts should be familiar with.

Chart Terminology

The following illustration depicts the terms used to describe chart elements.

The elements comprising a typical 2D chart

Unlike the other 2D chart types, pie charts contain the same elements but do not have axes.

Using the Property Editor

The JClass Chart Property Editor enables you to customize the properties of any chart.

A JClass Chart Property Editor and the chart it is associated with

Immediate Feedback Model

As you edit properties, the changes are immediately displayed. This enables you to quickly see how a change affects the chart so that you can make further changes without leaving the Property Editor.

Displaying the Property Editor At Run-Time

Position the mouse button over that part of the chart to modify. Click the right mouse button if you running Windows 95/NT, click the middle button if you are using a Unix OS, or click the button associated with launching a popup menu on your OS. A property editor that corresponding to the part of the chart to be edited appears, as shown in the previous illustration. Property editors are available for the Header, Legend, Footer, ChartArea and the Chart itself.

Note: The property editor is only available if you are running the Java Development Kit (JDK) 1.1 or later.

Editing Chart Properties

The following illustrates the steps required to edit the properties contained within a property editor at run time:

Select the tab that corresponds to the element of the chart that you want to edit.
Tabs contain one or more inner tabs that group related properties together. Some tabs also contain a list that selects a specific object to edit.
If the tab contains an tree control on the left side, select the specific object to edit from the tree.
Select the inner tab that corresponds to the kind of property you want to edit.
Click on a control and change the value of that property.
The change is immediately applied to the chart and displayed.
Make further changes to the same property or change other properties on this tab or other tabs.

Close-up of a sample property editor

Closing the Property Editor

Click the Close button to close the Property Editor.

Displaying the Editor at Design Time

Displaying the property editor at design-time depends on the Integrated Development Environment in use. Consult the IDE documentation for details. Note that the property pages may appear slightly differently in the IDE.

Sample property manager as seen within Borland's JBuilder IDE

Interacting with the Chart

You can interact with the chart as it is running to examine data more closely or visually isolate a part of the chart. Note that you can alter the settings, you cannot set them in place (i.e. you cannot write them to file). It is a good way to preview a Chart and alter its working parameters to achieve a more visually-appealing look. The following actions are possible:

moving the chart
zooming into or out of the chart
rotation (only for bar or pie charts that use the 3D display effect)
adding depth cues to the chart
use the pick feature to change the settings of data points.

It is also possible in most cases for the user to reset the chart to its original display parameters. The interactions described here effect the chart displayed inside the ChartArea; other chart elements like the header are not affected.

Note: The keyboard/mouse combinations that perform the different interactions can be changed or removed by a programmer. The interactions described here may not be enabled for your chart.

Choosing the Chart Type

JClass Chart can display data as one of five basic chart types: Plot, Scatter Plot, Bar, Stacking Bar and Pie. More specialized chart types, such as Hi-Lo or Gantt charts, can also be created using one of the basic five types.

Many more Chart types are under development. Contact KL Group for more details.

Plot Charts

Sample plot chart

A plot draws each series as connected points of data. By customizing the ChartStyle, you can remove the connecting lines to emphasize the data values themselves, or remove the points to emphasize the relationship between points. You can also customize the line and symbol properties of each series.

Scatter Plot Charts

Sample scatter plot chart

A scatter plot draws each series as points of data. Unlike plot charts, the data points are not connected.

Bar Charts

Sample bar chart

A bar chart draws each series as a bar in a cluster. The number of clusters is the number of points in the data series. Each cluster displays the nth data point in each series. Using ChartStyles, you customize the fill properties of each series. You can also customize bar cluster properties, set it so that it can be charted versus an axis representing a percentage between 0 and 100, and add 3D display properties using BarChartFormat.

Stacking Bar Charts

Sample stacking bar chart

A stacking bar chart draws each series as a portion of a stacked bar cluster, the number of clusters being the number of points in the data. Each bar displays the nth data point in each series. Using ChartStyles, you customize the fill properties of each series. You can also customize bar cluster properties and 3D display properties using BarChartFormat.

Pie Charts

Sample pie chart

A pie chart draws each datapoint as a slice in a pie. The number of pies is the number of points in the data series. Each pie displays the nth data point in each series. Using the ChartStyles property, you can customize the fill properties of each series. You can also customize special pie properties and 3D display properties using PieChartFormat.

Changing the chart type

In JClass Chart, the chart type is controlled by the data itself. Use the ChartType property to set the chart type for one ChartDataView.

Understanding Data Layout

JClass Chart employs a flexible data model that allows arbitrary data sources to be connected. Not every user wants to write an entire data source. To this end, several data sources are provided with JClass Chart:

InputStreamDataSource - accepts data from a stream
FileDataSource - reads data from a file
URLDataSource - reads data from a URL

These three data sources accept data in one of two basic layouts, Array and General.

Array Layout

Use Array layout with bar, stacking bar, and pie charts. Plot charts can also use Array data when the Y-values in their series share common X-values.

Sample array layout chart

The important Array layout characteristics illustrated above are:

The X-values of the points in each series are common to all series.
Each series contains the same number of points (although by using a data hole, a series can appear to have fewer points).

General Layout

Use General layout with plot charts. Bar, stacking bar, and pie charts cannot display General data.

Sample general layout chart

The important General layout characteristics illustrated above are:

The points in each series have their own X- and Y-values.
Each series can contain a different number of points.

1 Chart Basics