# mapplot

0th

Percentile

##### Trellis displays on Maps a.k.a. Choropleth maps

Produces Trellis displays of numeric (and eventually categorical) data on a map. This is largely meant as a demonstration, and users looking for serious map drawing capabilities should look elsewhere (see below).

Keywords
hplot
##### Usage
mapplot(x, data, ...)
"mapplot"(x, data, map, outer = TRUE, prepanel = prepanel.mapplot, panel = panel.mapplot, aspect = "iso", legend = NULL, breaks, cuts = 30, colramp = colorRampPalette(brewer.pal(n = 11, name = "Spectral")), colorkey = TRUE, ...)

prepanel.mapplot(x, y, map, ...)
panel.mapplot(x, y, map, breaks, colramp, exact = FALSE, lwd = 0.5, ...)
##### Arguments
x, y
For mapplot, an object on which method dispatch is carried out. For the formula method, a formula of the form y ~ x, with additional conditioning variables as desired. The extended form of conditioning using y ~ x1 + x2 etc. is also allowed. The formula might be interpreted as in a dot plot, except that y is taken to be the names of geographical units in map.

Suitable subsets (packets) of x and y are passed to the prepanel and panel functions.

data
A data source where names in the formula are evaluated
map
An object of class "map" (package maps), containing boundary information. The names of the geographical units must match the y variable in the formula.
outer
logical; how variables separated by + in the formula are interpreted. It is not advisable to change the default.
prepanel, panel
the prepanel and panel functions
aspect
aspect ratio
breaks, cuts, colramp
controls conversion of numeric x values to a false color. colramp should be a function that produces colors (such as cm.colors). If it is NULL, colors are taken from trellis.par.get("regions").
exact
the default exact = FALSE allows the given y values to match sub-regions of map, i.e. region names with a qualifier following ":", like "michigan:north", "michigan:south". These will both match a y value of "Michigan".
legend, colorkey
controls legends; usually just a color key giving the association between numeric values of x and color.
lwd
line width
...
Further arguments passed on to the underlying engine. See xyplot for details.
##### Value

An object of class "trellis".

##### Note

This function is meant to demonstrate how maps can be incorporated in a Trellis display. Users seriously interested in geographical data should consider using software written by people who know what they are doing.

##### References

Lattice

##### Aliases
• mapplot
• mapplot.formula
• panel.mapplot
• prepanel.mapplot
##### Examples
library(latticeExtra)  library(maps) library(mapproj) ## Note: Alaska, Hawaii and others are not included in county map; ## this generates warnings with both USCancerRates and ancestry. data(USCancerRates) suppressWarnings(print( mapplot(rownames(USCancerRates) ~ log(rate.male) + log(rate.female), data = USCancerRates, map = map("county", plot = FALSE, fill = TRUE, projection = "mercator")) )) suppressWarnings(print( mapplot(rownames(USCancerRates) ~ log(rate.male) + log(rate.female), data = USCancerRates, map = map("county", plot = FALSE, fill = TRUE, projection = "tetra"), scales = list(draw = FALSE)) )) data(ancestry) county.map <- map('county', plot = FALSE, fill = TRUE, projection = "azequalarea") ## set a sequential color palette as current theme, and use it opar <- trellis.par.get() trellis.par.set(custom.theme(region = brewer.pal(9, "Purples"), alpha.line = 0.5)) suppressWarnings(print( mapplot(county ~ log10(population), ancestry, map = county.map, colramp = NULL) )) trellis.par.set(opar) ## Not run: # # ## this may take a while (should get better area records) # # county.areas <- # area.map(county.map, regions = county.map$names, sqmi = FALSE) # # ancestry$density <- # with(ancestry, population / county.areas[as.character(county)]) # # mapplot(county ~ log(density), ancestry, # map = county.map, border = NA, # colramp = colorRampPalette(c("white", "black"))) # # ## End(Not run) 
Documentation reproduced from package latticeExtra, version 0.6-28, License: GPL (>= 2)

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