GEOG 414/514:  Advanced Geographic Data Analysis
Univariate plots

In describing or characterizing the observations of an individual variable, there are three basic properties that are of interest:

• the location of observations (along the number line in general (but the geographical analogy is obvious), or how large or small the values of the individual observations are)

• the dispersion (sometimes called scale) of the observations (how spread out they are along the number line, and again the geographical analogy is obvious)

• the distribution of the observations (a characterization of the frequency of occurrence of different values of the variable--do some values occurs more frequently than other values?)

Univariate plots provide one way to find out about those properties (and univariate descriptive statistics provide another).

There are two basic kinds of univariate, or one-variable-at-a-time plots,

1. Enumerative plots, or plots that show every observation, and

2. Summary plots, that generalize the data into a simplified representation.

Enumerative plot examples

Summary plot examples

Readings:  

Owen (The R Guide):  Ch. 4 & 5, section 6.3;  Kuhnert & Venebles (An Introduction...):  p. 61-76; Rossiter (Introduction ... ITC):  Ch. 2; sections 3.1-3.6