Show the data

Induce the viewer to think about the substance rather than about methodology, graphic design, the technology of graphic production, or something else

Avoid distorting what the data have to say

Present many numbers in a small space

Make large data sets coherent

Encourage the eye to compare different pieces of data

Reveal the data at several levels of detail, from a broad overview to the fine structure

Serve a reasonably clear purpose: description, exploration, tabulation, or decoration

Be closely integrated with the statistical and verbal descriptions of a data set.