Graphics Reference
In-Depth Information
boxplots, (ii) bivariate binned boxplots, (iii) time series plots, and (iv) line height
plots. he level
Omernik ecoregion micromaps involved large US regions, so re-
gion visibility was not a problem. However, highly detailed boundaries lead to a slow
graphics production. Faster production in the context of more numerous ecoregions
and over
US counties as opposed to
US states also motivated the develop-
ment of generalized micromaps. Geographers traditionally use the best encoding,
position along a scale, to show region boundaries. However, they also desire to show
statistics more precisely, and thus static LM plots soon appeared in the geographic
literature (Fonseca and Wong,
) as well.
Inthischapter,wecontinue withamotivational exampleinSect.
.
that showsthe
same data via choropleth mapsand LMplots. InSect.
.
,wediscussdesign issuesfor
LMplots andoutline their main purposes.All of theearly examples of LMplots were
created as static plots to be displayed as printed pages or as large posters. In Sect.
.
we discuss how micromaps can be used interactively on the Web. We return to pro-
duction resources for static LM plots via statistical sotware packages in Sect.
.
. We
finish with a discussion and comparison of LM plots with other graphical tools in
Sect.
.
.
A Motivational Example
1.2
Figure
.
shows two variables, the soybean yield and acreage from the
Cen-
sus of Agriculture for the US, displayed in two choropleth maps. Five equal-size
class intervals were chosen for each of the maps. A “
-class sequential
Greys” color
scheme,obtained fromhttp://colorbrewer.org and reprinted in Table
.
,was chosen,
with the lightest grey representing states where no soybeans were planted. he maps
in this figure were produced with the Geographic Information System (GIS) Arc-
View
.
. We obtained the data from the US Department of Agriculture-National
Agricultural Statistics Service (USDA-NASS) Web site http://www.nass.usda.gov/
research/apydata/soyapy.dat. Section
.
.
provides further details on these data and
the USDA-NASS Web site.
he two choropleth maps in Fig.
.
indicate that the highest yields and highest
acreages for soybeans occur in the Midwest. here seems to be some spatial trend,
i.e.,somesteadydecreaseforbothvariablesfromtheMidwesttotheSoutheast.Over-
Table
.
.
Values for the “
-class sequential
Greys”
color scheme, obtained from http://colorbrewer.org,
for use in ArcView
.
. Instead of breaking down the
range of possible values (
to
) into equally wide
intervals, the chosen values represent similar
perceptual differences. he first triple (
,
,
)
represents the lightest grey, the last triple (
,
,
)
the darkest grey. When represented as red, green,
and blue (RGB) values, the zeros will be replaced by
the nonzero value, i.e., (
,
,
) will become (
,
,
) and so on
Value
Value
Value
