quadrats

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Divide Region into Quadrats

Divides window into rectangular quadrats and returns the quadrats as a tessellation.

Keywords
utilities, datagen
Usage
quadrats(X, nx = 5, ny = nx, xbreaks = NULL, ybreaks = NULL, keepempty=FALSE)
Arguments
X
A window (object of class "owin") or anything that can be coerced to a window using as.owin, such as a point pattern.
nx,ny
Numbers of quadrats in the $x$ and $y$ directions. Incompatible with xbreaks and ybreaks.
xbreaks
Numeric vector giving the $x$ coordinates of the boundaries of the quadrats. Incompatible with nx.
ybreaks
Numeric vector giving the $y$ coordinates of the boundaries of the quadrats. Incompatible with ny.
keepempty
Logical value indicating whether to delete or retain empty quadrats. See Details.
Details

If the window X is a rectangle, it is divided into an nx * ny grid of rectangular tiles or `quadrats'.

If X is not a rectangle, then the bounding rectangle of X is first divided into an nx * ny grid of rectangular tiles, and these tiles are then intersected with the window X.

The resulting tiles are returned as a tessellation (object of class "tess") which can be plotted and used in other analyses.

If xbreaks is given, it should be a numeric vector giving the $x$ coordinates of the quadrat boundaries. If it is not given, it defaults to a sequence of nx+1 values equally spaced over the range of $x$ coordinates in the window X$window.

Similarly if ybreaks is given, it should be a numeric vector giving the $y$ coordinates of the quadrat boundaries. It defaults to a vector of ny+1 values equally spaced over the range of $y$ coordinates in the window. The lengths of xbreaks and ybreaks may be different.

By default (if keepempty=FALSE), any rectangular tile which does not intersect the window X is ignored, and only the non-empty intersections are treated as quadrats, so the tessellation may consist of fewer than nx * ny tiles. If keepempty=TRUE, empty intersections are retained, and the tessellation always contains exactly nx * ny tiles, some of which may be empty.

Value

  • A tessellation (object of class "tess") as described under tess.

See Also

tess, quadratcount, quadrat.test, quadratresample

Aliases
  • quadrats
Examples
W <- square(10)
 Z <- quadrats(W, 4, 5)
 plot(Z)

 data(letterR)
 plot(quadrats(letterR, 5, 7))
Documentation reproduced from package spatstat, version 1.21-0, License: GPL (>= 2)

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