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://geospatialpython.googlecode.com/svn/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:
First, we import the PyQt GUI library:
from PyQt4.QtGui import *Then, we load the layer:
lyr = QgsVectorLayer("/Users/joellawhead/qgis_data/ms/County10PopnHou.shp", "Population", "ogr")Next, we set up categories based on attribute names:
categories = [u'PCT_WHT', u'PCT_BLK', u'PCT_AMIND', u'PCT_ASIAN', u'PCT_HAW',...
