rsaga.inverse.distance {RSAGA}R Documentation

Spatial Interpolation Methods

Description

Spatial interpolation of point data using inverse distance to a power (inverse distance weighting, IDW), nearest neighbors, or modified quadratic shephard.

Usage

rsaga.inverse.distance(in.shapefile, out.grid, field, 
        power = 1, maxdist = 100, nmax = 10,
        target = rsaga.target(), ...)
rsaga.nearest.neighbour(in.shapefile, out.grid, field,
    target = rsaga.target(), ...)
rsaga.modified.quadratic.shephard(in.shapefile, out.grid, field,
    quadratic.neighbors = 13, weighting.neighbors = 19,
    target = rsaga.target(), ...)

Arguments

in.shapefile Input: point shapefile (default extension: .shp).
out.grid Output: filename for interpolated grid (SAGA grid file). Existing files will be overwritten!
field numeric(!): number (not name!) of attribute in the shapefile's attribute table to be interpolated; the first attribute is represented by a zero.
power numeric (>0): exponent used in inverse distance weighting (usually 1 or 2)
maxdist numeric: maximum distance of points to be used for inverse distance interpolation (search radius)
nmax Maximum number of nearest points to be used for interpolation
quadratic.neighbors integer >=5; ??
weighting.neighbors integer >=3; ??
target list: parameters identifying the target area, e.g. the lower left corner and size of grid, or name of a reference grid; see rsaga.target.
... Optional arguments to be passed to rsaga.geoprocessor, including the env RSAGA geoprocessing environment.

Details

Inverse distance weighting (IDW) uses module 0 in the SAGA library grid_gridding. Nearest neighbour interpolation uses module 1, and triangulation is performed by module 4.

Note

See the example section in the help file for write.shapefile in package shapefiles to learn how to apply these interpolation functions to a shapefile exported from a data.frame.

Modified Quadratic Shephard method: based on module 660 in TOMS (see references).

Author(s)

Alexander Brenning (R interface), Andre Ringeler and Olaf Conrad (SAGA modules)

References

QSHEP2D: Fortran routines implementing the Quadratic Shepard method for bivariate interpolation of scattered data (see R. J. Renka, ACM TOMS 14 (1988) pp.149-150). Classes: E2b. Interpolation of scattered, non-gridded multivariate data.

See Also

rsaga.ordinary.kriging, and idw in package gstat.


[Package RSAGA version 0.9-4 Index]