rsaga.grid.to.points: Convert SAGA grid file to point shapefile

In RSAGA: SAGA Geoprocessing and Terrain Analysis

Convert SAGA grid file to point shapefile

Description

Convert SAGA grid file to point (or polygon) shapefile - either completely or only a random sample of grid cells.

Usage

rsaga.grid.to.points(
  in.grids,
  out.shapefile,
  in.clip.polygons,
  exclude.nodata = TRUE,
  type = "nodes",
  env = rsaga.env(),
  ...
)

rsaga.grid.to.points.randomly(in.grid, out.shapefile, freq, ...)

Arguments

in.grids	Input: names of (possibly several) SAGA GIS grid files to be converted into a point shapefile.
out.shapefile	Output: point shapefile (default extension: .shp). Existing files will be overwritten!
in.clip.polygons	optional polygon shapefile to be used for clipping/masking an area
exclude.nodata	logical (default: TRUE), in newer SAGA versions numeric (see Note below): skip 'nodata' grid cells?
type	character string: "nodes": create point shapefile of grid center points; "cells" (only supported by SAGA GIS 2.0.6+): create polygon shapefile with grid cell boundaries
env	RSAGA geoprocessing environment created by rsaga.env(); required by rsaga.grid.to.points to determine version-dependent SAGA module name and arguments
...	Optional arguments to be passed to rsaga.geoprocessor()
in.grid	Input: SAGA grid file from which to sample.
freq	integer >=1: sampling frequency: on average 1 out of 'freq' grid cells are selected

Value

The type of object returned depends on the intern argument passed to the rsaga.geoprocessor(). For intern=FALSE it is a numerical error code (0: success), or otherwise (default) a character vector with the module's console output.

Note

These functions use modules ⁠Grid Cells to Points/Polygons⁠ (previously called ⁠Grid Values to Points⁠ and in some earlier versions ⁠Grid Values to Shapes⁠) and ⁠Grid Values to Points (randomly)⁠ in SAGA library shapes_grid.

The SAGA 2.0.6+ version of this module is more flexible as it allows to create grid cell polygons instead of center points (see argument type).

Since somewhere between SAGA 9.0.0 and 9.3.3, the NODATA argument is numeric with values of 0: include all cells, 1: include cell if at least one grid provides data, and 2: exclude cell if at least one grid does not provide data. From 9.3.0 up, exclude.nodata=TRUE is interpreted as (and converted to) 1.

Author(s)

Alexander Brenning (R interface), Olaf Conrad (SAGA modules)

See Also

rsaga.add.grid.values.to.points()

Examples

## Not run: 
# one point per grid cell, exclude nodata areas:
rsaga.grid.to.points("dem", "dempoints")
# take only every 20th point, but to not exclude nodata areas:
rsaga.grid.to.points.randomly("dem", "dempoints20", freq = 20)

## End(Not run)

RSAGA documentation built on April 3, 2025, 6:48 p.m.