GEOG 414/515:  Advanced Geographic Data Analysis
Descriptive plots and statistics for spatial data

There is a set of descriptive plots and statistics for spatial data that aims at displaying the same sort of information on location (or central tendency), dispersion (or scale or variability), and covariation (or association) that univariate and bivariate plots and descriptive statistics provide for intrinsically aspatial data.  

These statistics and plots are implemented in using several different package, including maptools, spdep, gstat, geoR, and fields, and these packages allow the results of data analyses to be easily mapped, and specifically spatial descriptive statistics and plots to be generated.

Basic statistics and plots

In addition to maps, a number of basic statistics and plots for spatial data can be obtained through the application of some of standard plotting functions and descriptive statistics.  Such plots are essentially aspatial, in the sense that they do not require specific locational or dimensional variables, but the locational variables can be used for conditioning, or for the construction of simple maps. 

• exploratory plot examples

Plots of Spatial Statistics (Variograms)

As might be expected given the greater implicit structure of spatial data (in contrast to regular or aspatial data), single-number statistics that describe the data--the variance or standard deviation, for example--are less interpretable.  However, insight can be gained by plotting multiple values of such statistics as a function of geographical location or distance.  When viewed in conjunction with a map, such plots can reveal additional structure in the data. 

• Variogram examples

Readings: 

O'Sullivan and Unwin (Geographic Information Analysis):  section 9.4