rasterizeWin: Rasterize points with a moving window

In terra: Spatial Data Analysis

Rasterize points with a moving window

Description

Rasterize points using a circle (or ellipse) as moving window. For each raster cell, the points (x, y) that fall within the window centered on that cell are considered. A function is used to compute a summary value (e.g. "mean") for the values (z) associated with these points.

This can result in much smoother results compared to the standard rasterize method.

Usage

## S4 method for signature 'SpatVector,SpatRaster'
rasterizeWin(x, y, field, win="circle", pars, fun, ..., cvars=FALSE, 
			  minPoints=1, fill=NA, filename="", wopt=list())

## S4 method for signature 'data.frame,SpatRaster'
rasterizeWin(x, y, win="circle", pars, fun, ..., cvars=FALSE, 
		      minPoints=1, fill=NA, filename="", wopt=list())

Arguments

x	SpatVector or matrix with at least three columns ((x, y) coordinates and a variable to be rasterized)
y	SpatRaster
field	character. field name in SpatVector x with the values to rasterize
win	character to choose the window type. Can be "circle", "ellipse", "rectangle", or "buffer"
pars	parameters to define the window. If win="circle" or win="buffer", a single number to set the radius of the circle or the width of the buffer. If win="ellipse", either two numbers (the x and y-axis) or three numbers the axes and a rotation (in degrees). If win="rectangle", either two (width, height) or three (width, height) and the rotation in degrees. The unit of the radius/width/height/axis parameters is that of the coordinate reference system (it is not expressed as cells). That is, if you have a lon/lat crs, there is no conversion of degrees to meters or vice-versa.
fun	function to summarize the values for each cell. If cvars=FALSE, functions must take a numeric vector and return (in all cases) one or more numbers. If cvars=TRUE, and multiple variables are used, the function must take a single argument (a data.frame with the names variables). For win="circle" and win="ellipse" there are two additional character values that can be used: "distto" (average distance to the points from the center of the cell) and "distbetween" (average distance between the points inside the window)
...	additional named arguments passed to fun
minPoints	numeric. The minimum number of points to use. If fewer points are found in a search ellipse it is considered empty and the fill value is returned
fill	numeric. value to use to fill cells with empty search areas
cvars	logical. When using multiple fields, should fun operate on all of them at once? If not, fun is applied to each variable separately
filename	character. Output filename
wopt	list with additional arguments for writing files as in writeRaster

Value

SpatRaster

See Also

rasterize, rasterizeGeom, interpNear, interpIDW

Examples

r <- rast(ncol=100, nrow=100, crs="local", xmin=0, xmax=50, ymin=0, ymax=50)
set.seed(100)
x <- runif(50, 5, 45)
y <- runif(50, 5, 45)
z <- sample(50)
xyz <- data.frame(x,y,z)

r <- rasterizeWin(xyz, r, fun="count", pars=5)

rfuns <- c("count", "min", "max", "mean")
x <- lapply(rfuns, function(f) rasterizeWin(xyz, r, fun=f, pars=5))
names(x) <- rfuns 
x <- rast(x)
#plot(x)

terra documentation built on Oct. 14, 2024, 5:07 p.m.