Description Usage Arguments Details Note Author(s) References See Also

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

1 2 3 4 5 6 7 8 9 10 11 12 | ```
rsaga.inverse.distance(in.shapefile, out.grid, field, power = 1, maxdist,
nmax = 100, target, env = rsaga.env(), ...)
rsaga.nearest.neighbour(in.shapefile, out.grid, field, target,
env = rsaga.env(), ...)
rsaga.modified.quadratic.shephard(in.shapefile, out.grid, field,
quadratic.neighbors = 13, weighting.neighbors = 19, target,
env = rsaga.env(), ...)
rsaga.triangulation(in.shapefile, out.grid, field, target,
env = rsaga.env(), ...)
``` |

`in.shapefile` |
Input: point shapefile (default extension: |

`out.grid` |
Output: filename for interpolated grid (SAGA grid file). Existing files will be overwritten! |

`field` |
numeric or character: number or 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); no search radius is applied when this argument is missing or equals |

`nmax` |
Maximum number of nearest points to be used for interpolation; |

`target` |
required argument of type list: parameters identifying the target area, e.g. the x/y extent and cellsize, or name of a reference grid; see |

`env` |
RSAGA geoprocessing environment created by |

`...` |
Optional arguments to be passed to |

`quadratic.neighbors` |
integer >=5; default 13. |

`weighting.neighbors` |
integer >=3; default 19. |

These functions use modules from the `grid_gridding`

SAGA GIS library. They do not support SAGA GIS 2.0.4, which differs in some argument names and parameterizations. Target grid parameterization by grid file name currently doesn't work with SAGA GIS 2.1.0 Release Candidate 1 (see also `rsaga.target()`

); stay tuned for future updates and fixes.

The 'Inverse Distance Weighted' module of SAGA GIS not only support inverse-distance weighted interpolation, but also exponential and other weighting schemes (command line argument WEIGHTING); these are however not accessible through this function, but only through the `rsaga.geoprocessor`

, if needed. See `rsaga.get.usage("grid_gridding","Inverse Distance Weighted")`

for details.

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).

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

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.

`rsaga.target()`

; idw() in package `gstat`

.

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