Book Image

QGIS Python Programming Cookbook

Book Image

QGIS Python Programming Cookbook

Overview of this book

Table of Contents (16 chapters)
QGIS Python Programming Cookbook
About the Author
About the Reviewers

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

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("/Users/joellawhead/qgis_data/ms/County10PopnHou.shp", "Population", "ogr")
  3. 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',...