# ellipse

0th

Percentile

##### 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.

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.

disc, owin.object, owin, as.mask

• ellipse
##### Examples
# NOT RUN {
W <- ellipse(a=5,b=2,centre=c(5,1),phi=pi/6)
plot(W,lwd=2,border="red")