Methods for Function elide in Package `maptools'

Methods for function elide to translate and disguise coordinate placing in the real world.

elide(obj, ...)
<!-- % (obj, bb=NULL, shift=c(0, 0), reflect=c(FALSE, FALSE), scale=NULL, flip=FALSE) -->

Methods

obj = "SpatialPoints"

elides object

obj = "SpatialPointsDataFrame"

elides object

obj = "SpatialLines"

elides object

obj = "SpatialLinesDataFrame"

elides object

obj = "SpatialPolygons"

elides object

obj = "SpatialPolygonsDataFrame"

elides object

Arguments

obj

object to be elided

...

other arguments:

bb

if NULL, uses bounding box of object, otherwise the given bounding box

shift

values to shift the coordinates of the input object; this is made ineffective by the scale argument

reflect

reverse coordinate axes

scale

if NULL, coordinates not scaled; if TRUE, the longer dimension is scaled to lie within [0,1] and aspect maintained; if a scalar, the output range of [0,1] is multiplied by scale

flip

translate coordinates on the main diagonal

rotate

default 0, rotate angle degrees clockwise around center

center

default NULL, if not NULL, the rotation center, numeric of length two

unitsq

logical, default FALSE, if TRUE and scale TRUE, impose unit square bounding box (currently only points)

Value

The methods return objects of the input class object with elided coordinates; the coordinate reference system is not set. Note that if the input coordinates or centroids are in the data slot data.frame of the input object, they should be removed before the use of these methods, otherwise they will betray the input positions.

Note

Rotation code kindly contributed by Don MacQueen

Examples

data(meuse)
coordinates(meuse) <- c("x", "y")
proj4string(meuse) <- CRS("+init=epsg:28992")
data(meuse.riv)
river_polygon <- Polygons(list(Polygon(meuse.riv)), ID="meuse")
rivers <- SpatialPolygons(list(river_polygon))
proj4string(rivers) <- CRS("+init=epsg:28992")
rivers1 <- elide(rivers, reflect=c(TRUE, TRUE), scale=TRUE)
meuse1 <- elide(meuse, bb=bbox(rivers), reflect=c(TRUE, TRUE), scale=TRUE)
opar <- par(mfrow=c(1,2))
plot(rivers, axes=TRUE)
plot(meuse, add=TRUE)
plot(rivers1, axes=TRUE)
plot(meuse1, add=TRUE)

par(opar)
meuse1 <- elide(meuse, shift=c(10000, -10000))
bbox(meuse)
#>      min    max
#> x 178605 181390
#> y 329714 333611
bbox(meuse1)
#>      min    max
#> x 188605 191390
#> y 319714 323611
rivers1 <- elide(rivers, shift=c(10000, -10000))
bbox(rivers)
#>        min      max
#> x 178304.0 182331.5
#> y 325698.5 337684.8
bbox(rivers1)
#>        min      max
#> x 188304.0 192331.5
#> y 315698.5 327684.8
meuse1 <- elide(meuse, rotate=-30, center=apply(bbox(meuse), 1, mean))
bbox(meuse)
#>      min    max
#> x 178605 181390
#> y 329714 333611
bbox(meuse1)
#>        min      max
#> x 179419.8 181278.9
#> y 329462.8 333890.2
plot(meuse1, axes=TRUE)