Graphical Display of Areas — area.plot • ade4

'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' (maptools package) and returns a data frame of type area.
area2poly takes an object of type 'area' and returns a list of class 'polylist'
area2link takes an object of type 'area' and returns a proximity matrix which terms are given by the length of the frontier between two polygons.
area.util.contour,area.util.xy and area.util.class are three utility functions.

Usage

area.plot(x, center = NULL, 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)
area2link(area)
area.util.contour(area)
area.util.xy(area)

Arguments

x: a data frame with three variables
center: a matrix with the same row number as x and two columns, the coordinates of polygone centers. If NULL, it is computed with area.util.xy
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 than 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.

Author

Daniel Chessel

Examples

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

par(mfrow = c(1, 1))

if (FALSE) { # \dontrun{
    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(1, 1))
    
    if(adegraphicsLoaded()) {
      if(requireNamespace("sp", quietly = TRUE)) {
        s.value(elec88$xy, elec88$tab, Sp = elec88$Spatial,
          method = "color", psub.text = names(elec88$tab), psub.cex = 3, 
          pSp.col = "white", pgrid.draw = FALSE, porigin.include = FALSE)
      }
    } else {
      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)
        }
      par(mfrow = c(1, 1))
    }
    
    if(!adegraphicsLoaded()) {
      data(irishdata)
      par(mfrow = c(2, 2))
      w <- ade4:::area.util.contour(irishdata$area)
      xy <- ade4:::area.util.xy(irishdata$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)
      par(mfrow = c(1, 1))

    }
} # }

data(irishdata)
w <- irishdata$area[c(42:53, 18:25), ]
w
#>    poly   x  y
#> 42  S07  16 50
#> 43  S07  16 44
#> 44  S07  44 47
#> 45  S07  21 34
#> 46  S07  20 20
#> 47  S07  28 19
#> 48  S07  46 23
#> 49  S07  30  8
#> 50  S07  45 12
#> 51  S07  68 35
#> 52  S07  68 59
#> 53  S07  63 78
#> 18  S04  68 35
#> 19  S04  68 59
#> 20  S04 112 55
#> 21  S04 119 50
#> 22  S04 132 25
#> 23  S04  74  0
#> 24  S04  45  0
#> 25  S04  45 12
w$poly <- as.factor(as.character(w$poly))
area.plot(w, clab = 2)
 
points(68, 59, pch = 20, col = "red", cex = 3)
points(68, 35, pch = 20, col = "red", cex = 3)
points(45, 12, pch = 20, col = "red", cex = 3)

sqrt((59 - 35) ^ 2) + sqrt((68 - 45) ^ 2 + (35 - 12) ^ 2)
#> [1] 56.52691
area2link(w)
#>          S07      S04
#> S07  0.00000 56.52691
#> S04 56.52691  0.00000