terra (version 1.6-17)

focalCor: Focal function across two layers

Description

Calculate values such as a correlation coefficient for focal regions in two neighboring layers. A function is applied to the first and second layer, then to the second and third layer, etc.

Usage

# S4 method for SpatRaster
focalCor(x, w=3, fun, ..., fillvalue=NA, 
		filename="", overwrite=FALSE, wopt=list())

Value

SpatRaster

Arguments

x

SpatRaster with at least two layers

w

window. The window can be defined as one (for a square) or two numbers (row, col); or with an odd-sized weights matrix. See the Details section in focal

fun

A function with at least two arguments (one for each layer)

...

additional arguments for fun

fillvalue

numeric. The value of the cells in the virtual rows and columns outside of the raster

filename

character. Output filename

overwrite

logical. If TRUE, filename is overwritten

wopt

additional arguments for writing files as in writeRaster

See Also

layerCor, focalReg, focal

Examples

r <- rast(system.file("ex/logo.tif", package="terra"))
set.seed(0)
r[[1]] <- flip(r[[1]], "horizontal")
r[[2]] <- flip(r[[2]], "vertical") + init(rast(r,1), runif)
r[[3]] <- init(rast(r,1), runif)

# suppress warning "the standard deviation is zero"
suppressWarnings(x <- focalCor(r, w=5, cor))

# this warning does not occur when using a larger window
x <- focalCor(r, w=9, function(x, y) cor(x, y))
plot(x)