# ellipse

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##### 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.

##### See Also

disc, owin.object, owin, as.mask

• ellipse
##### 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 1.37-0, License: GPL (>= 2)

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