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micromap: A Package for Linked Micromaps
Citation:
Payton, Q., M. McManus, M. Weber, Tony Olsen, AND Tom Kincaid. micromap: A Package for Linked Micromaps. Journal of Statistical Software. American Statistical Association, Alexandria, VA, 63(2):16, (2015).
Impact/Purpose:
This paper describes the micromap package developed for the statistical programming language R. The package provides a means to simultaneously summarize and display both statistical and geographic distributions by linking statistical summaries to a series of small maps. The R package allows for the convenient visualization of georeferenced statistics via linked micromaps, and will provide a useful means for displaying environmental, public health, agricultural and other types of data collected or aggregated over areal units such as states, counties, or watersheds.
Description:
The R package micromap is used to create linked micromaps, which display statistical summaries associated with areal units, or polygons. Linked micromaps provide a means to simultaneously summarize and display both statistical and geographic distributions by linking statistical summaries to a series of small maps. The package contains functions, heavily dependent on the utilities of the ggplot2 package, which may be used to produce a row-oriented graph composed of different panels, or columns, of information. These panels at a minimum contain maps, a legend, and statistical summaries. We first describe the layout of linked micromaps and then describe the structure required for both the spatial and statistical datasets. The function create map table in the micromap package creates the link between the two datasets, and relies on an sp spatial polygons data frame as input. Because highly detailed polygons are not appropriate for display in linked micromaps, we describe how polygon boundaries can be simplified, decreasing the time required to draw the graphs, while retaining adequate detail for detection of important features. Our worked examples of linked micromaps use public health data as well as environmental data collected from spatially balanced probabilistic surveys. This document is the primary reference for the R package micromap, and is available as a vignette in that the package.
