Rasterize points with a moving window

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

# S4 method for 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

See also

rasterize, rasterizeGeom, interpNear, interpIDW

Value

SpatRaster

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)