Pie Map

$image\piemap.gif$ Pie maps are used to represent multivariate data by drawing a proportionally sized pie chart for polygon, polyline, or point. Pie charts show two or more variables where each variable is represented by a proportionally sized slice of the pie. Up to 20 variables can be displayed on a pie map. Within a single pie, the size of the slices gives you the relative proportion of the values for that object. The entire pie chart is sized in relation to the total of all variables for a particular boundary, as compared to the totals of the variables for other boundaries. The position of the pies relative to the polygon, polyline, or point may be moved with the Move Centroids command.

For polygons, the pie charts are drawn at the area's centroid (geographic center). The areas use the default fill and line properties, or you can set unique fill and line properties for each area on the map.
For polylines, the pie charts are drawn at the midpoint along the polyline.
For points, the pie charts are drawn directly on top of the points.

Creating and Editing a Pie Map

Click the Map | Create Map | Pie command to create a pie map. Edit pie map properties in the Property Manager.

See Creating and Editing Thematic Maps for information on creating a pie map, changing a bar map to another map type, and changing map properties.

Pie Map Properties

The Property Manager for a pie map contains General, Data Labels, Info, Pies, 3D Settings, Pie Labels, and Map pages. Click the preceding hyperlinks for information on properties in each of the property manager pages.

Map Page

The Property Manager Map page has size, position, and display properties for a pie map.

Edit pie map properties in the Map page of the Property Manager.

General

The General section of the Map page has display options for the pie map. Click the Draw half pie check box to display a half pie chart. The half pie is not the default pie chart cut in half. Rather, in a half pie chart, the pie slices are proportions of half a circle, or cylinder for 3D pie charts.

Click the Map min radius & 3D height to a value of 0 to force the minimum radius or height to a data value of zero regardless of the data minimum.

Size

Change the pie map sizes in the Size section of the Map page. Select the feature of the pie map to vary with the data value in the Slice size list; click By percentage, By radius, or By radius and percentage. By percentage varies the area of the pie slices, and By radius varies the radius of the slices to represent the data value. When By percentage is selected the pie radius represents the total value of the pie. The By radius and By radius and percentage options only show the relationship of slices for each pie and does not show total pie values relative to each other.

Select Linear in the Proportional method list to scale the pie radiuses with the By percentage method, or slice radiuses with the By radius method, linearly between the minimum and maximum data values. Select Square root to scale the radii proportionally to the square root of the data values.

Set the Minimum radius and Maximum radius by typing a number in page units into the Minimum radius and Maximum radius fields. The radiuses can also be adjusted by clicking the buttons. When By percentage is the Slice size, the pie with the smallest total value is sized with the Minimum radius, and the pie with the largest total value is sized to the Maximum radius. The remaining pies are scaled between the two radiuses by the Propportional method. When By radius is selected, the smallest data value for each slice is represented by the Minimum radius, and the largest data value for each slice is represented by the Maximum radius. The remaining slices of each pie are scaled by the Proportional method.

Position

The centroid is the geographic center of an polygon, the midpoint along a polyline, or the location of a point. The centroid location can be moved for objects with the Move Centroids command. The Centroid offset is used to offset each pie from the centroid position. Center, Left, Right, Above, and Below position the pie in the specified direction. User defined enables the X offset and Y offset boxes so you can enter any offset amount. Type a value in page units into the X offset and Y offset fields or click the to set the offset values for a User defined Centroid offset.

Pie Line

Edit line properties for the lines between slices and around the circumference in the Pie line section of the Map page. See the line properties help page for more information on editing pie line properties.