Compare-methods: Compare-methods operations on GRasters and GRegions

In adamlilith/fasterRaster: Faster Raster and Spatial Vector Processing Using 'GRASS GIS'

Compare-methods operations on GRasters and GRegions

Description

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 signature 'GRaster,GRaster'
Compare(e1, e2)

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

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

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

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

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

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

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

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

## S4 method for signature '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)

}

adamlilith/fasterRaster documentation built on Sept. 23, 2024, 1:28 a.m.