Since every visualization starts with the data that is to be displayed, a ﬁrst
step in addressing the design of visualizations is to examine the character-
istics of the data. Data comes from many sources; it can be gathered from
sensors or surveys, or it can be generated by simulations and computations.
Data can be raw (untreated), or it can be derived from raw data via some
process, such as smoothing, noise removal, scaling, or interpolation. It also
can have a wide range of characteristics and structures.