R: Divide Region into Quadrats

quadrats {spatstat.geom} | R Documentation

## Divide Region into Quadrats

### Description

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

### 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 `Window(X)`.

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`.

### Author(s)

Adrian Baddeley Adrian.Baddeley@curtin.edu.au and Rolf Turner r.turner@auckland.ac.nz

### See Also

For calculations using quadrats, see `quadratcount`, `quadrat.test`, `quadratresample`

For other kinds of tessellations, see `tess`, `hextess`, `venn.tess`, `polartess`, `dirichlet`, `delaunay`, `quantess`, `bufftess` and `rpoislinetess`.

### Examples

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

     plot(quadrats(letterR, 5, 7))

[Package spatstat.geom version 2.3-2 Index]