Continuous scale or groups?
When a continuous numerical quantity is displayed on a map, a choice must be made about how to use colour to represent it.
Choose the colours for a map carefully.
In black-and-white publications, it is usually best to use group the values and use a small number of grey shades.
African life expectancy in 2005
The map below shows life expectancy varied in Africa in 2005.
Use the pop-up menu to investigate the use of different colours. Observe that:
The two choices Continuous yellow -> red -> blue and Five groups, smooth are probably the best colour representation.