ellipse
From spatstat v1.42-2
by Adrian Baddeley
Elliptical Window.
Create an elliptical window.
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, ifmask
isTRUE
. - 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 typepolygonal or of typemask ) specifying an elliptical window.
See Also
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)
Community examples
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