The Direction of Change map uses a classification scheme to indicate specific type of change over time (e.g. Low to High, High to Low, etc. ). This map uses the rate classifications on the comparison maps to determine if a pixel value should be classified into the high or low, greater than expected and lower than expected groups. The map is a pixel by pixel comparison to determine the value of a pixel in both time periods and classify it according to the following groups. Blue areas are those that had a lower than expected classification for both time periods, Green areas are those that were high in the first time period and are lower than expected in the second time period, Yellow areas are those which had a greater than expected classification for both time periods, while Red areas are those which were lower than expected in the first time period and in the second time period became greater than expected.
Data Sources: Cancer incidence data from the State Health Registry of Iowa. 1:100,000 Digital Raster Graphic from the Iowa Geographic Image Map Server hosted by Iowa State University. County borders from the Natural Resources GIS Library hosted by the Iowa Department of Natural Resources and the US Geological Survey.
Created by David Haynes, Kirsten Beyer, Gerard Rushton at the University of Iowa Department of Geography, software by Chetan Tiwari at the University of North Texas, June 2009..