R: Geographic distance

distance {terra} | R Documentation

## Geographic distance

### Description

If `x` is a SpatRaster:

If `y` is `missing` this method computes the distance, for all cells that are `NA` in SpatRaster `x` to the nearest cell that is not `NA`. If argument `grid=TRUE`, the distance is computed using a path that goes through the centers of the 8 neighboring cells.

If `y` is a SpatVector, the distance to that SpatVector is computed for all cells. For lines and polygons this is done after rasterization; and only the overlapping areas of the vector and raster are considered (for now).

If `x` is a SpatVector:

If `y` is `missing`, a distance matrix between all object in `x` is computed. An distance matrix object of class "dist" is returned.

If `y` is a SpatVector the geographic distance between all objects is computed (and a matrix is returned). If both sets have the same number of points, and `pairwise=TRUE`, the distance between each pair of objects is computed, and a vector is returned.

### Usage

    ## S4 method for signature 'SpatRaster,missing'
    distance(x, y, grid=FALSE, filename="", ...)

    ## S4 method for signature 'SpatRaster,SpatVector'
    distance(x, y, filename="", ...)

    ## S4 method for signature 'SpatVector,ANY'
    distance(x, y, sequential=FALSE, pairs=FALSE, symmetrical=TRUE)

    ## S4 method for signature 'SpatVector,SpatVector'
    distance(x, y, pairwise=FALSE)

    ## S4 method for signature 'matrix,matrix'
    distance(x, y, lonlat, pairwise=FALSE)

    ## S4 method for signature 'matrix,ANY'
    distance(x, y, lonlat, sequential=FALSE)

### Arguments

`x` | SpatRaster, SpatVector, or two-column matrix (x,y) or (lon,lat)
`y` | missing or SpatVector, or two-column matrix
`grid` | logical. If `TRUE`, distance is computed using a path that goes through the centers of the 8 neighboring cells
`filename` | character. Output filename
`...` | additional arguments for writing files as in `writeRaster`
`sequential` | logical. If `TRUE`, the distance between sequential geometries is returned
`pairwise` | logical. If `TRUE` and if x and y have the same size (number of rows), the pairwise distances are returned instead of the distances between all elements
`lonlat` | logical. If `TRUE` the coordinates are interpreted as angular (longitude/latitude). If `FALSE` they are interpreted as planar
`pairs` | logical. If `TRUE` a "from", "to", "distance" matrix is returned
`symmetrical` | logical. If `TRUE` and `pairs=TRUE`, the distance between a pair is only included once. The distance between geometry 1 and 3 is included, but the (same) distance between 3 and 1 is not

### Value

SpatRaster or numeric or matrix or distance matrix (object of class "dist")

### Note

The distance unit is in meters.

A distance matrix can be coerced into a matrix with `as.matrix`

### Examples

    #lonlat
    r <- rast(ncols=36, nrows=18, crs="+proj=longlat +datum=WGS84")
    r[500] <- 1
    d <- distance(r)
    plot(d / 100000)

    #planar
    r <- rast(ncols=36, nrows=18, crs="+proj=utm +zone=1 +datum=WGS84")
    r[500] <- 1
    d <- distance(r)

    p1 <- vect(rbind(c(0,0), c(90,30), c(-90,-30)), crs="+proj=longlat +datum=WGS84")
    dp <- distance(r, p1)

    d <- distance(p1)
    d
    as.matrix(d)

    p2 <- vect(rbind(c(30,-30), c(25,40), c(-9,-3)), crs="+proj=longlat +datum=WGS84")
    dd <- distance(p1, p2)
    dd
    pd <- distance(p1, p2, pairwise=TRUE)
    pd
    pd == diag(dd)

    # polygons, lines
    crs <- "+proj=utm +zone=1"
    p1 <- vect("POLYGON ((0 0, 8 0, 8 9, 0 9, 0 0))", crs=crs)
    p2 <- vect("POLYGON ((5 6, 15 6, 15 15, 5 15, 5 6))", crs=crs)
    p3 <- vect("POLYGON ((2 12, 3 12, 3 13, 2 13, 2 12))", crs=crs)
    p <- rbind(p1, p2, p3)
    L1 <- vect("LINESTRING(1 11, 4 6, 10 6)", crs=crs)
    L2 <- vect("LINESTRING(8 14, 12 10)", crs=crs)
    L3 <- vect("LINESTRING(1 8, 12 14)", crs=crs)
    lns <- rbind(L1, L2, L3)
    pts <- vect(cbind(c(7,10,10), c(3,5,6)), crs=crs)

    distance(p1,p3)
    distance(p)
    distance(p,pts)
    distance(p,lns)
    distance(pts,lns)

[Package terra version 1.4-7 Index]