R: Convert Data To Class owin

as.owin {spatstat.core} | R Documentation

## Convert Data To Class owin

### Description

Converts data specifying an observation window in any of several formats, into an object of class `"owin"`.

### Usage

     ## S3 method for class 'ppm'
    as.owin(W, ..., from=c("points", "covariates"), fatal=TRUE)

     ## S3 method for class 'kppm'
    as.owin(W, ..., from=c("points", "covariates"), fatal=TRUE)

     ## S3 method for class 'dppm'
    as.owin(W, ..., from=c("points", "covariates"), fatal=TRUE)

     ## S3 method for class 'msr'
    as.owin(W, ..., fatal=TRUE)

     ## S3 method for class 'quadrattest'
    as.owin(W, ..., fatal=TRUE)

     ## S3 method for class 'rmhmodel'
    as.owin(W, ..., fatal=FALSE)

### Arguments

`W` | Data specifying an observation window, in any of several formats described under Details below.
`fatal` | Logical value determining what to do if the data cannot be converted to an observation window. See Details.
`...` | Ignored.
`from` | Character string. See Details.

### Details

The class `"owin"` is a way of specifying the observation window for a point pattern. See `owin.object` for an overview.

The generic function `as.owin` converts data in any of several formats into an object of class `"owin"` for use by the spatstat package. The function `as.owin` is generic, with methods for different classes of objects, and a default method.

The argument `W` may be

- an object of class `"owin"`

- a structure with entries `xrange`, `yrange` specifying the x and y dimensions of a rectangle

- a structure with entries named `xmin`, `xmax`, `ymin`, `ymax` (in any order) specifying the x and y dimensions of a rectangle. This will accept objects of class `bbox` in the `sf` package.

- a numeric vector of length 4 (interpreted as `(xmin, xmax, ymin, ymax)` in that order) specifying the x and y dimensions of a rectangle

- a structure with entries named `xl`, `xu`, `yl`, `yu` (in any order) specifying the x and y dimensions of a rectangle as `(xmin, xmax) = (xl, xu)` and `(ymin, ymax) = (yl, yu)`. This will accept objects of class `spp` used in the Venables and Ripley spatial package.

- an object of class `"ppp"` representing a point pattern. In this case, the object's `window` structure will be extracted.

- an object of class `"psp"` representing a line segment pattern. In this case, the object's `window` structure will be extracted.

- an object of class `"tess"` representing a tessellation. In this case, the object's `window` structure will be extracted.

- an object of class `"quad"` representing a quadrature scheme. In this case, the window of the `data` component will be extracted.

- an object of class `"im"` representing a pixel image. In this case, a window of type `"mask"` will be returned, with the same pixel raster coordinates as the image. An image pixel value of `NA`, signifying that the pixel lies outside the window, is transformed into the logical value `FALSE`, which is the corresponding convention for window masks.

- an object of class `"ppm"`, `"kppm"` or `"dppm"` representing a fitted point process model. In this case, if `from="data"` (the default), `as.owin` extracts the original point pattern data to which the model was fitted, and returns the observation window of this point pattern. If `from="covariates"` then `as.owin` extracts the covariate images to which the model was fitted, and returns a binary mask window that specifies the pixel locations.

- A `data.frame` with exactly three columns. Each row of the data frame corresponds to one pixel. Each row contains the x and y coordinates of a pixel, and a logical value indicating whether the pixel lies inside the window.

- A `data.frame` with exactly two columns. Each row of the data frame contains the x and y coordinates of a pixel that lies inside the window.

- an object of class `"distfun"`, `"nnfun"` or `"funxy"` representing a function of spatial location, defined on a spatial domain. The spatial domain of the function will be extracted.

- an object of class `"rmhmodel"` representing a point process model that can be simulated using `rmh`. The window (spatial domain) of the model will be extracted. The window may be `NULL` in some circumstances (indicating that the simulation window has not yet been determined). This is not treated as an error, because the argument `fatal` defaults to `FALSE` for this method.

- an object of class `"layered"` representing a list of spatial objects. See `layered`. In this case, `as.owin` will be applied to each of the objects in the list, and the union of these windows will be returned.

- an object of class `"SpatialPolygon"`, `"SpatialPolygons"` or `"SpatialPolygonsDataFrame"`. To handle these data types, the package maptools must be loaded, because it provides the methods for `as.owin` for these classes. For full details, see `vignette('shapefiles')`.

If the argument `W` is not in one of these formats and cannot be converted to a window, then an error will be generated (if `fatal=TRUE`) or a value of `NULL` will be returned (if `fatal=FALSE`).

When `W` is a data frame, the argument `step` can be used to specify the pixel grid spacing; otherwise, the spacing will be guessed from the data.

### Value

An object of class `"owin"` (see `owin.object`) specifying an observation window.

### Author(s)

Adrian Baddeley Adrian.Baddeley@curtin.edu.au, Rolf Turner r.turner@auckland.ac.nz and Ege Rubak rubak@math.aau.dk.

### See Also

`owin.object`, `owin`.

Additional methods for `as.owin` are provided in the maptools package: `as.owin.SpatialPolygon`, `as.owin.SpatialPolygons`, `as.owin.SpatialPolygonsDataFrame`.

### Examples

     w <- as.owin(c(0,1,0,1))
     w <- as.owin(list(xrange=c(0,5),yrange=c(0,10)))
     # point pattern
     data(demopat)
     w <- as.owin(demopat)
     # image
     Z <- as.im(function(x,y) { x + 3}, unit.square())
     w <- as.owin(Z)

[Package spatstat.core version 2.0-0 Index]