ellipse

From spatstat v1.42-2 by Adrian Baddeley

Elliptical Window.

Create an elliptical window.

Keywords: spatial, datagen

Usage

ellipse(a, b, centre=c(0,0), phi=0, ..., mask=FALSE, npoly = 128)

Arguments

a,b: The half-lengths of the axes of the ellipse.
centre: The centre of the ellipse.
phi: The (anti-clockwise) angle through which the ellipse should be rotated (about its centre) starting from an orientation in which the axis of half-length a is horizontal.
mask: Logical value controlling the type of approximation to a perfect ellipse. See Details.
...: Arguments passed to as.mask to determine the pixel resolution, if mask is TRUE.
npoly: The number of edges in the polygonal approximation to the ellipse.

Details

This command creates a window object representing an ellipse with the given centre and axes.

By default, the ellipse is approximated by a polygon with npoly edges.

If mask=TRUE, then the ellipse is approximated by a binary pixel mask. The resolution of the mask is controlled by the arguments ... which are passed to as.mask.

The arguments a and b must be single positive numbers. The argument centre specifies the ellipse centre: it can be either a numeric vector of length 2 giving the coordinates, or a list(x,y) giving the coordinates of exactly one point, or a point pattern (object of class "ppp") containing exactly one point.

Value

An object of class owin (either of type polygonal or of type mask) specifying an elliptical window.

Examples

W <- ellipse(a=5,b=2,centre=c(5,1),phi=pi/6)
  plot(W,lwd=2,border="red")
  WM <- ellipse(a=5,b=2,centre=c(5,1),phi=pi/6,mask=TRUE,dimyx=512)
  plot(WM,add=TRUE,box=FALSE)

Documentation reproduced from package spatstat, version 1.42-2, License: GPL (>= 2)

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