## PieChart: Minimum Specification

The minimum specification for a PieChart requires a valid data model. Generally the data model should assign the Category variable role to a ClassificationVariable in the model, but if the role is not assigned, the PieChart automatically assigns it to the first string column found in the data model, or to the first numeric column if the model has no string column. If the Response variable role is not assigned, the pie slices represent the Category variable's frequency count.

Example
Basic Requirements for Creating a PieChart: Swing-based code, Servlet-based code

## PieChart: Functional Overview

The Independent variable(s) in the chart are treated as Classification variables. Each category of the Independent variable is displayed as an instance of a Pie slice. Basic statistics such as Sum, Mean, and Frequency are supported, and you can control the labels that are displayed for each variable.

The component can display charts in 2D or 3D view and can display the chart as a solid pie or a pie with a donut hole in the middle. It can use the values of a subgroup variable to display multiple, concentric pie charts, and it can use the values of multiple response variables to display a separate chart for each unique group value. Finally, the component can use the values of multiple classification variables, producing separate charts for the additional values. The multiple charts can be arranged in columns (using the ColumnVariable role), rows (using the RowVariable role), or a graph matrix (using both roles). A separate chart is generated for each unique column or row value, or for each value pair when both a column and row variable are specified. You can control the arrangement and text of the labels and values that identify the column and row axes.

## PieChart: Data Access

A pie chart's data properties are defined in a data model that descends from PieChartDataModel, an abstract class whose subclasses provide a handle to the data and determine the number and arrangement of data elements (pie slices). PieChartDataModel has the following subclasses:

- PieChartTableDataModel models relational data from a Swing TableModel and maps the data columns to the graph.
- PieChartOLAPDataModel models OLAP data through a com.sas.storage.olap.OLAPDataSetInterface.

## PieChart: Display Properties

A PieChart's individual display properties can be set by calling the PieChart's getGraphModel() method, which returns a PieChartModel that can be used to set the desired properties. The PieChartModel class contains

- PieChart-specific properties
- Common graph properties
- A collection of models that control the appearance of the graph's peripheral elements, such as its legend.

Although modifying the PieChartModel provides considerable control, it can be tedious to modify properties individually. For example, graphs distinguish between different types of text, such as label text, value text, data-label text, and title text. Whereas the PieChartModel can independently control these different text types, doing so requires you to apply the same properties to all applicable locations.

An easier way to set a PieChart's display properties is to apply a pre-defined GraphStyle to the chart. A graph style sets many of the graph's visual characteristics, such as its use of colors, fonts, background, transparency, drop shadows, and more. A graph style can be used as is or modified through the GraphStyle class.

A graph style can be specified as an argument on a PieChart's constructor. Or, it can be applied to an existing chart by calling the PieChart's applyGraphStyle() method as follows:

    PieChart pieChart = new PieChart();
    pieChart.applyGraphStyle(new GraphStyle(GraphStyle.STYLE_SCIENCE);

Applying a GraphStyle to a graph propagates the GraphStyle's properties onto all applicable graph properties, including those in the graph model.

Rather than use the style as is, you can modify it before applying it. Modifying the style definition is typically easier and more convenient than modifying the graph's individual display properties. For example, the GraphStyle class contains only a single set of value text propertes. After applying the modified style, you can still adjust individual properties through the graph model.

The following code fragment modifies a graph style before applying it to a pie chart.

    // Create and modify a graph style
    GraphStyle graphStyle = new GraphStyle(GraphStyle.STYLE_SCIENCE);
       graphStyle.getValueTextStyle().setColor(Color.darkGray);
       graphStyle.getValueTextStyle().setFont(new java.awt.Font("Arial",Font.BOLD,14));

    // Apply the modified graph style to a chart
    PieChart pieChart = new PieChart();
       pieChart.applyGraphStyle(graphStyle);

Whether you set a graph style or individual display properties, the new display settings override any previous settings that were applied to the graph. For example, if a gray background and yellow slice outlines have been set on a graph, and then a style is applied to that same graph, the style's background and outline settings replace the previously set gray background and yellow outlines.

## PieChart: Titles and Footnotes

The PieChart component supports four titles and two footnotes, each with its own display attributes. To display multiple lines of text with the same attributes, use the line-end character (\n) in the specified text string.

To assign a title or footnote,

- Create a NoteModel to encapsulate a text value with associated display attributes
- Assign the model to the chart by calling one of the PieChart's setTitle() or setFootnote() methods.

The easiest way to set the text for a title or footnote is to get the chart's title or footnote property and set its text as follows:

    pieChart.getTitle1().setText("Line One\nLine Two");

To change the text attributes for a title or footnote, set the attributes on a NoteModel and assign the NoteModel to the appropriate title or footnote. The following example sets the title "Product Revenue" and displays it in blue, using a 24-point TimesRoman font with a drop shadow.

    NoteModel myTitle = new NoteModel( "Product Revenue" );
    myTitle.getTextStyle().setColor(Color.blue);
    myTitle.getTextStyle().setFont(new java.awt.Font("TimesRoman",Font.PLAIN,24));
    myTitle.getTextStyle().getShadowStyle().setVisible(true);

    // Create the graph and assign the title
    PieChart pieChart = new PieChart();
    pieChart.setTitle1( myTitle );

## PieChart: Usage Examples

The following example fragment graphs product revenue. It uses relational data from a Swing TableModel that contains a string column of Product IDs and a numeric column of product Revenues. To enhance the graph's appearance, the example assigns the Magnify GraphStyle to the chart.

    javax.swing.table.TableModel mySalesData = <...>;

    // Create the PieChart's data model.
    PieChartTableDataModel pieChartDataModel = new PieChartTableDataModel( mySalesData );
    pieChartDataModel.setCategoryVariable( new ClassificationVariable("Product") );
    pieChartDataModel.setResponseVariable( new AnalysisVariable("Revenue") );

    // Create the PieChart applying the data model and the "Magnify" GraphStyle
    PieChart pieChart = new PieChart( pieChartDataModel, new GraphStyle(GraphStyle.STYLE_MAGNIFY) );
    pieChart.setTitle1( new NoteModel("Product Revenue") );
    pieChart.setFootnote1( new NoteModel("Company Confidential") );

Assuming the TableModel also contains a column named Year (numeric or string) that identifies the year, and a column named ProductType (numeric or string) that identifies the product type, the following example organizes the graph by year and product type:

    javax.swing.table.TableModel mySalesData = <...>;

    // Create the PieChart's data model.
    PieChartTableDataModel pieChartDataModel = new PieChartTableDataModel( mySalesData );
    pieChartDataModel.setColumnVariable( new ClassificationVariable("Year") );
    pieChartDataModel.setRowVariable( new ClassificationVariable("ProductType") );
    pieChartDataModel.setCategoryVariable( new ClassificationVariable("Product") );
    pieChartDataModel.setResponseVariable( new AnalysisVariable("Revenue") );

    // Create the PieChart applying the data model and the "Magnify" GraphStyle
    PieChart pieChart = new PieChart( pieChartDataModel, new GraphStyle(GraphStyle.STYLE_MAGNIFY) );
    pieChart.setTitle1( new NoteModel("Product Revenue") );
    pieChart.setTitle2( new NoteModel("By Year and Product Type") );
    pieChart.setFootnote1( new NoteModel("Company Confidential") );

Assuming the TableModel also contains a numeric data column named PredictedRevenue for predicted revenue, the following example compares predicted revenue to actual revenue by product organized by year and product type:

    javax.swing.table.TableModel mySalesData = <...>;

    // Create the PieChart's data model.
    PieChartTableDataModel pieChartDataModel = new PieChartTableDataModel( mySalesData );
    pieChartDataModel.setColumnVariable( new ClassificationVariable("Year") );
    pieChartDataModel.setRowVariable( new ClassificationVariable("ProductType") );
    pieChartDataModel.setCategoryVariable( new ClassificationVariable("Product") );
    pieChartDataModel.setResponseVariable( new AnalysisVariableList(
      new String[] {"PredictedRevenue", "Revenue"} ) );

    // Create the PieChart applying the data model and the "Magnify" GraphStyle
    PieChart pieChart = new PieChart( pieChartDataModel, new GraphStyle(GraphStyle.STYLE_MAGNIFY) );
    pieChart.setTitle1( new NoteModel("Predicted Revenue vs Actual Revenue") );
    pieChart.setTitle2( new NoteModel("By Year and Product Type") );
    pieChart.setFootnote1( new NoteModel("Company Confidential") );

## PieChart: Behavior

The PieChart asynchronously updates when a PropertyChangeEvent is received from any of its models (DataModel, GraphModel or NoteModels).