Not every plot shows individual observations. Some plots, such as histograms, bar charts, and mosaic plots, aggregate observations into a group and represent that group with a bar or box. The discussion in this section applies to plots that show individual markers.
When a graph is printed on a gray-scale printer, it is often easier to discern observations that have different marker shapes than it is to discern markers that have different colors. Even on a computer screen, marker shape is sometimes preferred for classifying markers according to a small number of discrete values. For example, marker shape is an ideal way to encode gender.
You can change the marker shape for all observations, or just for observations that are selected. You can select observations by using graphical techniques or by using the Find dialog box in a data table, as discussed in the section Finding Observations.