compare-generics: Compare and logical methods

In terra: Spatial Data Analysis

Compare and logical methods

Description

Standard comparison and logical operators for computations with SpatRasters. Computations are local (applied on a cell by cell basis). If multiple SpatRasters are used, these must have the same geometry (extent and resolution). These operators have been implemented:

Logical: !, &, |, isTRUE, isFALSE

Compare: ==, !=, >, <, <=, >=, is.na, is.nan, is.finite, is.infinite

See not.na for the inverse of is.na, and noNA to detect cells with missing value across layers.

The compare and logic methods implement these operators in a method that can return NA istead of FALSE and allows for setting an output filename.

The terra package does not distinguish between NA (not available) and NaN (not a number). In most cases this state is represented by NaN.

If you use a SpatRaster with a vector of multiple numbers, each element in the vector is considered a layer (with a constant value). If you use a SpatRaster with a matrix, the number of columns of the matrix must match the number of layers of the SpatRaster. The rows are used to match the cells. That is, if there are two rows, these match cells 1 and 2, and they are recycled to 3 and 4, etc.

The following method has been implemented for (SpatExtent, SpatExtent): ==

Usage

## S4 method for signature 'SpatRaster'
compare(x, y, oper, falseNA=FALSE, filename="", overwrite=FALSE, ...)

## S4 method for signature 'SpatRaster'
logic(x, oper, falseNA=FALSE, filename="", overwrite=FALSE, ...)

Arguments

x	SpatRaster
y	SpatRaster or numeric
oper	character. Operator name. For compare this can be one of "==", "!=", ">", "<", ">=", "<=" and for logic it can be one of "!", "is.na", "allNA", "noNA", "is.infinite", "is.finite", "iSTRUE", "isFALSE"
falseNA	logical. Should the result be TRUE, NA instead of TRUE, FALSE?
filename	character. Output filename
overwrite	logical. If TRUE, filename is overwritten
...	additional arguments for writing files as in writeRaster

Value

SpatRaster or SpatExtent

See Also

all.equal, Arith-methods. See ifel to conveniently combine operations and Math-methods or app to apply any R function to a SpatRaster.

Examples

r1 <- rast(ncols=10, nrows=10)
values(r1) <- runif(ncell(r1))
r1[10:20] <- NA
r2 <- rast(r1)
values(r2) <- 1:ncell(r2) / ncell(r2)

x <- is.na(r1)
!x
r1 == r2 
compare(r1, r2, "==")
compare(r1, r2, "==", TRUE)

terra documentation built on Oct. 14, 2024, 5:07 p.m.