A choropleth map is a thematic map in which areas are shaded or patterned in proportion to the measurement of the statistical variable being displayed on the map.
The choropleth maps are great to visually show relevant information within a map in a single look.
To do choropleth map (also known as thematic or data maps) with QGIS 2.4 you must:
- Choose the layer (shape is the most common kind of layer to do that) that have the data you want to use.
- Go to properties -> Style
- Change the upper pull-down menu to graduated (if data is numeric) or categorized (if data is not numeric)
- You must choose the base attribute
- If data is numeric you must select the number of clases (number of elements of the gradient), the color ramp and the mode that the gradient will be done.
- If data is not numeric, you must add manually every symbol-value match to do the categorization.
- You can change the shape and other parameters of the symbols that you will use.
And thats all! You’ll have a beautiful thematic map based on your data.