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) -->

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)

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)

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

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")
#> Warning: Discarded datum Amersfoort in Proj4 definition
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)