In the Using WFS spatial filters recipe, Chapter 1, Working with Vectors, you created a thematic map by classifying the features contained in the countries layer according to the continent they belong. You used an opaque fill for this map.
However, when dealing with statistical data, it is more appropriate to use a dot density chart.
Note
A dot density chart is an often used way to represent data on a map. For a general introduction, have a look at http://en.wikipedia.org/wiki/Dot_distribution_map.
You will again use the countries layer and will classify features according to population.
Open the CSS Style section from the GeoServer web interface. Then, select the Choose a different layer link. From the list of layers, select the countries layer.
Select the link Create a new style. In the form, select the NaturalEarth workspace and insert
DotDensityas the style name.Replace...