Cartogram Map

Cartogram maps display variables by varying area size. MapViewer's can create Dorling, contiguous, and noncontiguous cartograms. In a Dorling cartogram the areas are replaced by circles and the circles are scaled according to a variable. The maps can be controlled so the circles do not overlap and are positioned as close to the base map's centroids as possible. In a noncontiguous cartogram, polygon shapes are disconnected, and the area is proportional to the selected variable. In a contiguous cartogram, polygons remain connected, and their size and shape are distorted as the area is scaled to the selected variable.

Creating and Editing a Cartogram Map

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

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

Cartogram Map Properties

The cartogram map Property Manager has General, Data Labels, Info, and Map pages. Click the preceding hyperlinks for information on properties in each of the property manager pages.

Map Page

Select cartogram type and edit cartogram specific properties in the Map page of the Property Manager.

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

General

The General section properties select the cartogram type and edit the cartogram map. Click the Cartogram type list to select a Dorling, Non-contiguous, or Contiguous cartogram.

Generating a contiguous cartogram map can take a few seconds, depending on the cartogram map settings, data set, and your computer's capabilities. Unlike other gridding operations, contiguous cartogram map creation cannot be cancelled.

The Leaping force controls the distance the circles or polygons move in each convergence pass. The circles or polygons move away from the previous position with each pass. Type a value between 0.01 and 1.00 in the Leaping force field or click the buttons to set the Leaping force. A Leaping force of 1.0 moves the circle far away from the previous position with each pass. A Leaping force of 0.01moves the circles very little with each pass. Dorling and Non-contiguous cartograms have the Leaping force property.

The A/R ratio is the attraction/repulsion ratio that controls circle or polygon overlap. Type a value between 0.01 and 1.00 in the A/R ratio field or click the buttons to set the A/R ratio. An A/R ratio of 1.0 makes the circles overlap each other. An A/R Ratio of 0.01 leads to minimum overlap. Dorling and Non-contiguous cartograms have the A/R ratio property.

Convergence passes controls the number of times the circles are repositioned with the Leaping force and A/R ratio values. Only Dorling cartograms have the Convergence passes property.

Click the Defaluts button in the Default settings field to return the cartogram to the MapViewer defaults. Only Dorling and Non-contiguous cartograms have the Defalut settings option.

Line

Set the line properties for the cartogram map in the Line section. See the line properties help page for more information on editing cartogram line properties.

Fill

Set the cartogram fill properties in the Fill section. See the fill properties help page for more information on editing cartogram map fill properties. Apply a gradient fill to the cartogram map by selecting Linear or Radial from the Type list. Click on the Colormap selection to pick a predefined colormap for the gradient, or click the button to create a custom colormap in the Colormap dialog. Select a Vertical, Horizontal, Inward, or Outward gradient direction in the Gradient Direction list.