Fuzzy mode

For each point, the number of points (itself and coincident ones included) within distance r of it. With r = 0 it counts coincident points, the mode of exact locations; with r > 0 it is the fuzzy mode of the crime-mapping literature, a fixed-radius scan centred on each incident. Counts of nearby points overlap by design: each point counts its own neighbourhood.

Usage

fzmode(x, y = NULL, r, count = NULL, metric = "euclid", lonlat = FALSE)

Arguments

x, y

The points: x and y numeric vectors of equal length; or x a matrix or data frame with columns named x and y (or X and Y, as sf::st_coordinates() names them, or lon and lat with lonlat = TRUE) and y NULL; or x an sf or sfc object of POINT geometries, whose coordinate reference system must agree with lonlat. An unnamed two-column matrix is read as x then y; other columns are never taken by position. Vectors given separately (x, y, and w or t where a function takes them) are matched by name when every one is named and no name repeats, as elsewhere in the package; otherwise by position. No missing or infinite values.

r

The radius: one number from 0, in the unit of the coordinates (metres when lonlat = TRUE). Distances up to and including r count.

count

NULL for points, or for zones: one whole count from 0 per zone (x, y the zones' centroids); the result is then each zone's total count within r of it, its own included.

metric

The distance: "euclid" or "manhattan" (|dx| + |dy|), as in spwt() and jtsurf().

lonlat

FALSE (the default) when x and y are planar coordinates in one length unit; TRUE when they are longitude and latitude in degrees, which are then projected to metres by eqproj() about their own centre, and centres are returned in degrees. It is never guessed.

Value

An integer vector, one count per point, in input order (with count, a numeric vector of zone totals).

References

Eck, J. E., Chainey, S., Cameron, J. G., Leitner, M. and Wilson, R. E. (2005). Mapping Crime: Understanding Hot Spots. National Institute of Justice, NCJ 209393.

Examples

fzmode(c(0, 0, 1, 5), c(0, 0, 0, 5), r = 1)
#> [1] 3 3 3 1