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Compare-methods operations on GRasters and GRegions

Source: R/07_comparison.r
Compare-methods.Rd

You can do comparative operations on GRasters using normal operators in R: <, <=, ==, !=, >=, and >. You can also use %in% for categorical GRasters (see vignette("GRasters", package = "fasterRaster")).

You can also compare two GRegions using the == and != operators. Most users of fasterRaster will not have to work much with "regions" (see vignette("regions", package = "fasterRaster")), so can ignore this functionality. GRegions are the same if they have the same coordinate reference system, location/project and mapset (see vignette("projects_mapsets", package = "fasterRaster")), topology (2D or 3D), extent, and resolution. If both are 3D, then they must also have the same vertical extent and number of depths.

Usage

# S4 method for class 'GRaster,GRaster'
Compare(e1, e2)

# S4 method for class 'logical,GRaster'
Compare(e1, e2)

# S4 method for class 'GRaster,logical'
Compare(e1, e2)

# S4 method for class 'numeric,GRaster'
Compare(e1, e2)

# S4 method for class 'GRaster,numeric'
Compare(e1, e2)

# S4 method for class 'GRaster,integer'
Compare(e1, e2)

# S4 method for class 'integer,GRaster'
Compare(e1, e2)

# S4 method for class 'GRaster,character'
Compare(e1, e2)

# S4 method for class 'character,GRaster'
Compare(e1, e2)

# S4 method for class 'GRegion,GRegion'
Compare(e1, e2)

Arguments

e1, e2

Values depend on the type of comparison:

  • Comparing GRasters to logical, numeric, character values: e1 and e2 can be any one of these. Comparison to a character string can be useful when using a categorical raster, in which case you can use something like raster1 == "Wetlands" to coerce all "wetland" cells to be 1 (TRUE) and all others 0 (FALSE) or NA (if it was originally NA).

  • Comparing a GRegion to another GRegion: e1 and e2 must be GRegions!

Value

Comparing GRasters: An "integer" GRaster with values of 0 (FALSE), 1 (TRUE), or NA (neither).

Comparing GRegions: Output is logical.

Examples

if (grassStarted()) {

# Setup
library(terra)

# Example data
madElev <- fastData("madElev")

# Convert a SpatRaster to a GRaster
elev <- fast(madElev)
elevs <- c(elev, elev, log10(elev) - 1, sqrt(elev))
names(elevs) <- c("elev1", "elev2", "log_elev", "sqrt_elev")

elev
elevs

# Comparisons
elev < 100
elev <= 100
elev == 100
elev != 100
elev > 100
elev >= 100

elev + 100 < 2 * elev

elevs > 10
10 > elevs

# logic
elev < 10 | elev > 200
elev < 10 | cos(elev) > 0.9

elev < 10 | TRUE
TRUE | elev > 200

elev < 10 | FALSE
FALSE | elev > 200

elev < 10 & cos(elev) > 0.9

elev < 10 & TRUE
TRUE & elev > 200

elev < 10 & FALSE
FALSE & elev > 200

}