Square pie charts (a.k.a. waffle charts) can be used
to communicate parts of a whole for categorical quantities. To emulate the
percentage view of a pie chart, a 10x10 grid should be used with each square
representing 1% of the total. Modern uses of waffle charts do not
necessarily adhere to this rule and can be created with a grid of any
rectangular shape. Best practices suggest keeping the number of categories
small, just as should be done when creating pie charts. Tools are provided
to create waffle charts as well as stitch them together, and to use glyphs
for making isotype pictograms.