ade4 (version 1.01)

area.plot: Graphical Display of Areas

Description

'area' is a data frame with three variables. The first variable is a factor defining the polygons. The second and third variables are the xy coordinates of the polygon vertices in the order where they are found.

area.plot : grey levels areas mapping

poly2area takes an object of class 'polylist' (spdep package, that contains the older package 'spweights') and returns a data frame of type area. area2poly takes an object of type 'area' and returns a list of class 'polylist' area.util.contour and area.util.xy are two utility functions.

Usage

area.plot(x, values = NULL, graph = NULL, lwdgraph = 2,
nclasslegend = 8, clegend = 0.75, sub = "", csub = 1, 
possub = "topleft", cpoint = 0, label = NULL, clabel = 0, ...)
area2poly(area)
poly2area (polys)

Arguments

x

a data frame with three variables

values

if not NULL, a vector which values will be mapped to grey levels. The values must be in the same order as the values in unique(x.area[,1])

graph

if not NULL, graph is a neighbouring graph (object of class "neig") between polygons

lwdgraph

a line width to draw the neighbouring graph

nclasslegend

if value not NULL, a number of classes for the legend

clegend

if not NULL, a character size for the legend, used with par("cex")*clegend

sub

a string of characters to be inserted as sub-title

csub

a character size for the sub-titles, used with par("cex")*csub

possub

a string of characters indicating the sub-titles position ("topleft","topright","bottomleft","bottomright")

cpoint

if positive, a character size for drawing the polygons vertices (check up), used with par("cex")*cpoint

label

if not NULL, by default the levels of the factor that define the polygons are used as labels. To change this value, use label. These labels must be in the same order as unique(x.area[,1])

clabel

if not NULL, a character size for the polygon labels, used with par("cex")*clabel

polys

a list belonging to the 'polylist' class in the spdep package

area

a data frame of class 'area'

...

further arguments passed to or from other methods

Value

• poly2area returns a data frame 'factor,x,y'. area2poly returns a list of class polylist.

Examples

data(elec88)
par(mfrow = c(2,2))
area.plot(elec88$area, cpoint = 1)
area.plot(elec88$area, lab = elec88$lab, clab = 0.75)
area.plot(elec88$area, clab = 0.75)
# elec88$neig <- neig(area = elec88$area)
area.plot(elec88$area, graph = elec88$neig, 
sub = "Neighbourhood graph", possub = "topright")

par(mfrow = c(3,3))
for (i in 1:9) {
    x <- elec88$tab[,i]
    area.plot(elec88$area, val=x,
    sub = names(elec88$tab)[i], csub = 3, cleg = 1.5)
}

par(mfrow = c(3,3))
for (i in 1:9) {
    x <- elec88$tab[,i]
    s.value(elec88$xy, elec88$tab[,i], contour = elec88$contour,
    meth = "greylevel", sub = names(elec88$tab)[i], csub = 3, 
    cleg = 1.5, incl = FALSE)
}

data(irishdata)
par(mfrow = c(2,2))
w <- area.util.contour(irishdata$area)
xy <- area.util.xy(irishdata$area)
area.plot(irishdata$area, cpoint = 1)
apply(w, 1, function(x) segments(x[1],x[2],x[3],x[4], lwd = 3))
area.plot(irishdata$area, clabel = 1)
s.label(xy, area = irishdata$area, incl = FALSE, clab = 0, 
cpoi = 3, addax = FALSE, contour = w)
s.label(xy, area = irishdata$area, incl = FALSE, 
addax = FALSE, contour = w)
if (require(spdep, quiet = TRUE)) {
    data(columbus)
    par(mfrow = c(2,2))
    plot(col.gal.nb, coords, pch = 20, cex = 2)
    col.gal.neig <- nb2neig(col.gal.nb)
    s.label(data.frame(coords), neig = col.gal.neig,
    inc = FALSE, addax = FALSE, clab = 0, cneig = 1, cpo = 2)
    plotpolys(polys,bbs)
    area.plot(poly2area(polys))

    # 1
    crime.f <- as.ordered(cut(columbus$CRIME,
    breaks = quantile(columbus$CRIME, probs = seq(0,1,0.2)),
    include.lowest = TRUE))
    colours <- c("salmon1", "salmon2", "red3", "brown", "black")
    plot(bbs[,1], bbs[,4], xlab = "", ylab = "", asp = 1, type = "n",
    xlim = range(c(bbs[,1], bbs[,3])), ylim = range(c(bbs[,2], bbs[,4])))
    for (i in 1:length(polys)) 
    polygon(polys[[i]], col = colours[codes(crime.f[i])])
    legend(x = c(6, 7.75), y = c(13.5, 15), legend = levels(crime.f),
    fill = colours, cex = 0.7)
    title(sub = paste("Columbus OH: residential burglaries and ",
    "vehicle
thefts", "per thousand households, 1980"))
    
    # 2
    area1 <- poly2area(polys)
    w <- area.util.contour(area1)
    wxy <- area.util.xy(area1)
    area.plot(area1, values = columbus$CRIME, sub = paste("Columbus ",
    "OH: residential burglaries and vehicle
thefts",
    "per thousand households, 1980"))
    apply(w, 1, function(x) segments(x[1], x[2], x[3], x[4], lwd = 2))

    # 3
    data(elec88)
    fr.area <- elec88$area
    fr.xy <- area.util.xy(fr.area)
    fr.neig <- elec88$neig # neig(area = fr.area)

    # 4
    fr.poly <- area2poly(fr.area)
    fr.nb <- neig2nb(fr.neig)
    plotpolys(fr.poly, attr(fr.poly, "region.rect"), border = "grey")
    plot(fr.nb, fr.xy, add = TRUE)
    s.label(fr.xy, clab = 0, area = fr.area, neig = fr.neig, 
    cneig = 1, cpo = 2, inc = FALSE, addax = FALSE)
}
par(mfrow = c(1,1))