Focal weights matrix

Calculate focal ("moving window") weight matrix for use in the focal function. The sum of the values adds up to one.

Usage

focalWeight(x, d, type=c('circle', 'Gauss', 'rectangle'), fillNA=FALSE)

Arguments

x

Raster* object

d

numeric. If type=circle, the radius of the circle (in units of the CRS). If type=rectangle the dimension of the rectangle (one or two numbers). If type=Gauss the size of sigma, and optionally another number to determine the size of the matrix returned (default is 3 times sigma)

type

character indicating the type of filter to be returned

fillNA

logical. If TRUE, zeros are set to NA such that they are ignored in the computations. Only applies to type="circle"

Value

matrix that can be used in focal

Examples

r <- raster(ncols=180, nrows=180, xmn=0, crs="+proj=utm +zone=1")
# Gaussian filter for square cells
gf <- focalWeight(r, .5, "Gauss")
focalWeight(r, 2, "circle", fillNA=TRUE)
#>            [,1]       [,2]       [,3]       [,4]       [,5]
#> [1,]         NA         NA 0.07692308         NA         NA
#> [2,]         NA 0.07692308 0.07692308 0.07692308         NA
#> [3,] 0.07692308 0.07692308 0.07692308 0.07692308 0.07692308
#> [4,]         NA 0.07692308 0.07692308 0.07692308         NA
#> [5,]         NA         NA 0.07692308         NA         NA