Using pie charts for symbols

QGIS has the ability to use dynamic pie charts as symbols describing the statistics in a given region. In this recipe, we'll use pie chart symbols on a polygon layer in QGIS.

Getting ready

For this recipe, download the following zipped shapefile and extract it to a directory named ms in your qgis_data directory from https://github.com/GeospatialPython/Learn/raw/master/County10PopnHou.zip.

How to do it...

As with other renderers, we will build a symbol layer, add it to a renderer, and display the layer on the map. The pie chart diagram renderers are more complex than other renderers but have many more options. Perform the following steps to create a pie chart map:

1. First, we import the PyQt GUI library:

           from PyQt4.QtGui import * 
   

2. Then, we load the layer:

           lyr = QgsVectorLayer("/qgis_data/ms/County10PopnHou.shp",
                                "Population", "ogr") 
   

3. Next, we set up categories based on attribute names:

      ...