gris-package: gris: A flexible geometry data model for R.

In r-gris/gris: A Flexible Geometry and Topology Model for Spatial Data in R

Description

The gris package provides a relational table model for spatial vector data in R. Spatial vector data are topology-based discrete spatial units such as areas (including polygons), lines and points.

Details

These kinds of data are defined in many different ways in various R packages, but the sp package has provided the most comprehensive and standard model to match the traditional GIS layer forms.

Gris features

• provide a clear decoupling of topology from geometry (see section "Gris topology" below)

• transcend the X/Y-only limitation for vertex attributes

• allow multiple topological types in individual layers (i.e. Manifold or MapInfo drawings)

• provide a flexible basis for conversion between other formats and domain-specific structures

I. Creation

gris.Spatial	create from Spatial*DataFrame
grisFromRasterGeom	create from geom format
grisFromFortify	create from fortify format
as.gris.triangulation	create from triangulation

II. Plotting

plot.gris	plot a gris object as polypath, lines, points, or triangles
plot3d.gris	plot a gris object in 3d

III. Manipulation

[.gris	extract a subset of a gris object
pointInTriangle	identify which triangle points fall in

IV. Conversion to other types

as.SpatialPolygonsDataFrame.gris	coerce to SpatialPolygonsDataFrame, SpatialLinesDataFrame, SpatialPointsDataFrame, SpatialMultiPointsDataFrame
triangulate.gris	add triangle primitives to a gris object

V. Miscellaneous

brick2col	create hex value colours from an RGB RasterBrick

Gris topology

Topology defines the way that space is filled by 0D (points), 1D (lines), 2D (areas - or polygons) objects. (Higher dimensional topologies are possible but not explored yet.)

Geometry defines an actual instantiation of an object in a given coordinate system.

Examples of the difference are

• polygons defining continental outlines on the Earth, these shapes are 2D topologically, but geometrically can be plotted in the plane (in long-lat, or projected coordinates) or "draped" around a curve, such as the Earth as a globe or across a topographic landscape

• lines defining animal tracks in space time, these 1D shapes can have geometric vertex attributes such as X, Y, Z, time, temperature, etc.

Topology dimension may be 0D, 1D, 2D, or higher and geometry dimension is not necessarily coupled to this, or restricted to 2D.

Note that certain degeneracies are possible and may be important. A time series of point estimates in space may not have any sensible geometric values at all, but the topological description provided by that time series is a real structure.

r-gris/gris documentation built on May 14, 2019, 12:57 a.m.