More on thematic maps

Objectives

• Return exams
• More about classification of choropleth maps
• Time issues

Notes on the Exam

Overall scores: very spread out. Mean 56, mode, 56, max. 91, min 21

PLEASE do not panic! The conversion from points to grades will be lenient.

Some observations:

• Knowing and understanding terms and language
• Reading the WHOLE question
• How we will proceed from here.

Classification of choropleth maps

As explained last time, a choropleth map usually converts a continuous attribute (such as a derived ratio - population denisty, percent graduated from high school, etc.) to a set of ordered classes (a class is a category in a classification...).

Techniques for classification:

• Equal intervals
  • Take the maximum and minimum (usually the actual ones, but sometimes the theoretically possible), divide this distance along the attribute into even segments.
• Quantiles
  • Place an even number of objects (data points) into each class. Usually makes uneven distance along the number line.
• "Natural Breaks"
• Specific thresholds (values that make sense for that attribute)
  • Growth rate of zero
  • Freezing water makes 32 degrees F of interest
  • Ratio of males to females at 100 per 100 females

Time

Maps of change