Share a Scale or a Legend If Possible
Sharing a scale or a legend saves screen space. Users find it easier to compare values that use the same scale and to compare graphs that use the same mapping of colors to categories. Of course, graphs can only share a single scale if they show quantities in the same range and units, and they can only share a legend if they show the same set of categories. If you need multiple gauges, consider using a gauge set, which is designed to allow multiple gauges to share a single scale and legend.
Support Comparisons of Similarly Transformed Data
Presenting data in a form that supports comparison can be misleading if the data has not been collected, measured, or transformed in a consistent manner. When users need to compare data that has been collected over time periods of different lengths, be sure to label the differences clearly.
Use the Same Graph Types If Possible
Users find it easier to compare graphs of the same type than graphs that are of different types. For example, instead of using a bar graph and a pie chart, consider using two bar graphs.
Check That Colors and Other Settings Are Used Consistently
While most graph settings are determined automatically for OBIEE applications, extra care is needed to ensure that the default settings for individual graphs minimize meaningless visual differences between multiple graphs. Users comparing graphs expect that visual differences will be significant. For example, if one graph uses a certain color to display a particular category, make sure that category is displayed with the same color in every other graph on the page. Check that similar colors are used to indicate similar categories.
You many need to override other settings for graphs that display different amounts of data. For example, when using two pie charts , users may be confused if one pie has labeled slices, while another does not. Users may also be confused if the pies themselves are different sizes.