Creating pie graphs

A pie graph consists of a circle ("pie") divided into two or more sections (slices or wedges). Pie graphs emphasize where your data fits in relation to a larger whole and are particularly useful for showing proportions and ratios. Pie graphs work best when your data consists of several large categories (three to seven categories), too many categories will divide the pie into small segments that are difficult to interpret.

Controlling pie graphs

If you have a table of the human cases of avian flu virus by country in a table, in the order of when the virus was first discovered (from 1997 to December 2005), the pie graph will have the wedges in the same order as they are in the table:

Pie graph table and default sort order

If you want to have the wedges in the graph sorted in order of size from largest to smallest, set the Sort field to Cases and the sort type to Descending. The default label field is <None>, but to see the name of the country instead, set the Label field to the Country text field (see the left figure below). Alternatively, to have the wedges in alphabetical order by the country name, set the Sort field to Country (right figure below).

Pie graph sorted by size and by string

Selections on pie graphs

Only a single wedge can be selected on pie graphs. It is not possible to dynamically select multiple adjacent wedges with a selection marquee or with a shift-click action. The selection point will be based on the cursor location where the mouse button was released.

  1. Click the View menu, point to Graphs, then click Create.
  2. Click the Graph type drop-down arrow and choose the Pie type Pie.
  3. Click the Layer/Table drop-down arrow and choose the layer or table containing the data values that are to be graphed.
  4. Click the Value field drop-down arrow and choose the field of values to graph. The wizard shows the initial version of the graph.
  5. The wedges of the graph are initially displayed with the first data value starting at the three o'clock position and subsequent values plotting as subsequent wedges in the counterclockwise direction. Sort the wedges in an ascending or descending order based on another field with the Sort field.
    Sort field
  6. Specify a different field with which to label the wedges in the graph in Label field, commonly a text (string) field.
  7. By default, the values of the input data are added to the legend of the graph. Uncheck the Add to legend check box to disable this.
  8. Check the Show labels (marks) check box to see the wedges in the pie labeled with their actual values. This is useful when there are wedges of similar size, where the small difference in their size may not be easily seen.
  9. Change the color of the wedges in the graph with the Color control.
  10. To create partial instead of full circles for the pies,reduce the Total Pie angle setting from the default of 360°.
    Total Pie angle
  11. Adjust in degrees the starting point of the pie graph from its default three o'clock position with the Rotate Pie control.
  12. Highlight the largest single wedge of the pie with the Explode the biggest slice (%)control.
  13. Uncheck the Show border check box to remove the outline of the pie and all of the wedges.
  14. Click Next to proceed to the general properties page to complete your graph.

Related Topics

Published 6/7/2010