spatstat.geom (version 3.3-3)

persp.ppp: Perspective Plot of Marked Point Pattern

Description

For a spatial point pattern with numeric marks, generate a perspective plot in which each data point is shown as a vertical spike, with height proportional to the mark value.

Usage

# S3 method for ppp
persp(x, ..., main, grid = TRUE, ngrid = 10,
            col.grid = "grey", col.base = "white",
            win.args=list(), spike.args = list(), neg.args = list(),
            which.marks = 1, zlab = NULL, zlim = NULL, zadjust = 1)

Value

(Invisibly) the perspective transformation matrix.

Arguments

x

A spatial point pattern (object of class "ppp") with numeric marks, or a data frame of marks.

...

Additional graphical arguments passed to persp.default to determine the perspective view (for example the rotation angle theta and the elevation angle phi) or passed to segments to control the drawing (for example lwd for line width).

main

Optional main title for the plot.

grid

Logical value specifying whether to draw a grid of reference lines on the horizontal plane.

ngrid

Number of grid lines to draw in each direction, if grid=TRUE. An integer, or a pair of integers specifying the number of grid lines along the horizontal and vertical axes respectively.

col.grid

Colour of grid lines, if grid=TRUE.

col.base

Colour with which to fill the horizontal plane.

win.args

List of arguments passed to plot.owin to control the drawing of the window of x. Applicable only when the window is not a rectangle.

spike.args

List of arguments passed to segments to control the drawing of the spikes.

neg.args

List of arguments passed to segments applicable only to those spikes which have negative height (corresponding to a mark value which is negative).

which.marks

Integer, or character name, identifying the column of marks which should be used, when marks(x) is a data frame.

zlab

Optional. Label for the vertical axis. Character string or expression.

zlim

Optional. Range of values on the vertical axis. A numeric vector of length 2.

zadjust

Scale adjustment factor controlling the height of spikes.

Author

Adrian Baddeley.

Details

The function persp is generic. This is the method for spatial point patterns (objects of class "ppp"). The argument x must be a point pattern with numeric marks, or with a data frame of marks.

A perspective view will be plotted. The eye position is determined by the arguments theta and phi passed to persp.default.

First the horizontal plane is drawn in perspective view, using a faint grid of lines to help suggest the perspective. Next the observation window of x is placed on the horizontal plane and its edges are drawn in perspective view. Finally for each data point in x, a vertical spike is erected at the spatial location of the data point, with height equal to the mark value of the point.

If any mark values are negative, the corresponding spikes will penetrate below the horizontal plane. They can be drawn in a different colour by specifying neg.args as shown in the examples.

Like all spatial plots in the spatstat family, persp.ppp does not independently rescale the \(x\) and \(y\) coordinates. A long narrow window will be represented as a long narrow window in the perspective view. To override this and allow the coordinates to be independently rescaled, use the argument scale=TRUE which will be passed to persp.default.

Examples

   persp(longleaf, theta=-30, phi=35, spike.args=list(lwd=3), zadjust=1.5)

   # negative mark values
   X <- longleaf
   marks(X) <- marks(X) - 20
   persp(X, theta=80, phi=35, neg.args=list(col="red"),
         spike.args=list(lwd=3), zadjust=1.2)

   # irregular window
   Australia <- Window(austates)
   Y <- runifrect(70, Frame(Australia))[Australia]
   marks(Y) <- runif(npoints(Y))
   persp(Y, theta=30, phi=20, col.base="lightblue",
         win.args=list(col="pink", border=NA),
         spike.args=list(lwd=2), zadjust=1.5)