R: Difference of Disc Areas

areaGain {spatstat.geom} | R Documentation

## Difference of Disc Areas

### Description

Computes the area of that part of a disc that is not covered by other discs.

### Usage

       areaGain(u, X, r, ..., W=as.owin(X), exact=FALSE,
                         ngrid=spatstat.options("ngrid.disc"))

### Arguments

`u` | Coordinates of the centre of the disc of interest. A vector of length 2. Alternatively, a point pattern (object of class `"ppp"`).
`X` | Locations of the centres of other discs. A point pattern (object of class `"ppp"`).
`r` | Disc radius, or vector of disc radii.
`...` | Arguments passed to `distmap` to determine the pixel resolution, when `exact=FALSE`.
`W` | Window (object of class `"owin"`) in which the area should be computed.
`exact` | Choice of algorithm. If `exact=TRUE`, areas are computed exactly using analytic geometry. If `exact=FALSE` then a faster algorithm is used to compute a discrete approximation to the areas.
`ngrid` | Integer. Number of points in the square grid used to compute the discrete approximation, when `exact=FALSE`.

### Details

This function computes the area of that part of the disc of radius `r` centred at the location `u` that is not covered by any of the discs of radius `r` centred at the points of the pattern `X`. This area is important in some calculations related to the area-interaction model `AreaInter`.

If `u` is a point pattern and `r` is a vector, the result is a matrix, with one row for each point in `u` and one column for each entry of `r`. The `[i,j]` entry in the matrix is the area of that part of the disc of radius `r[j]` centred at the location `u[i]` that is not covered by any of the discs of radius `r[j]` centred at the points of the pattern `X`.

If `W` is not `NULL`, then the areas are computed only inside the window `W`.

### Value

A matrix with one row for each point in `u` and one column for each value in `r`.

### Author(s)

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

### See Also

`AreaInter`, `areaLoss`

### Examples

       u <- c(0.5,0.5)
       areaGain(u, cells, 0.1)

[Package spatstat.geom version 2.2-0 Index]