Compare-methods operations on GRasters and GRegions

You can do comparative operations on GRasters using normal operators in R: <, <=, ==, !=, >=, and >. You can also use %in% for categorical GRasters.

You can also compare two GRegions using the == and != operators. Most users of fasterRaster will not have to work much with regions, so can ignore this functionality. GRegions are the same if they have the same coordinate reference system, location and mapset, 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(sf)
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

# do some math
elev + 100
elev - 100
elev * 100
elev / 100
elev ^ 2
elev %/% 100 # divide then round down
elev %% 100 # modulus

100 + elev
100 %/% elev
100 %% elev

elevs + 100
100 + elevs

# math with logicals
elev + TRUE
elev - TRUE
elev * TRUE
elev / TRUE
elev ^ TRUE
elev %/% TRUE # divide then round down
elev %% TRUE # modulus

elevs + TRUE
TRUE + elevs

# Raster interacting with raster(s):
elev + elev
elev - elev
elev * elev
elev / elev
elev ^ log(elev)
elev %/% sqrt(elev) # divide then round down
elev %% sqrt(elev) # modulus

elevs + elev
elev * elevs

# sign
abs(-1 * elev)
abs(elevs)

# powers
sqrt(elevs)

# trigonometry
sin(elev)
cos(elev)
tan(elev)

asin(elev)
acos(elev)
atan(elev)

atan(elevs)
atan2(elev, elev^1.2)
atan2(elevs, elev^1.2)
atan2(elev, elevs^1.2)
atan2(elevs, elevs^1.2)

# logarithms
exp(elev)
log(elev)
ln(elev)
log2(elev)
log1p(elev)
log10(elev)
log10p(elev)
log(elev, 3)

log(elevs)

# rounding
round(elev + 0.5)
floor(elev + 0.5)
ceiling(elev + 0.5)
trunc(elev + 0.5)

# comparison
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

# Mathematical functions on GRasters with >= 2 layers:
mean(elevs)
mmode(elevs)
median(elevs)
nunique(elevs)

sum(elevs)
count(elevs)
min(elevs)
max(elevs)
range(elevs)
skewness(elevs)
kurtosis(elevs)

which.min(elevs)
which.max(elevs)

slope(elevs)
intercept(elevs)
r2(elevs)
tvalue(elevs)

stdev(elevs)
stdev(elevs, pop = FALSE)
var(elevs)
varpop(elevs)

# Note: To get quantiles for each layer, use
# global(x, "quantile", probs = 0.2).
quantile(elevs, 0.1)

}