trim: Remove rows and columns from a raster that are all NA

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

Remove rows and columns from a raster that are all NA

Description

This function removes any rows and columns from a GRaster that are all NA.

If the GRaster is a stack of rasters, then the rasters will all be trimmed to the same extent such that none have any rows or columns that are all NA. In other words, if at least one raster in the stack has a non-NA cell in a row or column, all rasters will retain that row or column.

Usage

## S4 method for signature 'GRaster'
trim(x, pad = 0)

Arguments

x	A GRaster.
pad	Numeric integer: Number of NA rows and columns to retain. The default is 0.

Value

A GRaster.

See Also

terra::trim(), extend(), and GRASS module g.region

Examples

if (grassStarted()) {

# Setup
library(terra)

# Elevation raster
madElev <- fastData("madElev")

# Convert SpatRaster to a GRaster:
elev <- fast(madElev)

# Trim NA rows/columns:
trimmedElev <- trim(elev)
dim(elev)
dim(trimmedElev)

# Trim a "stack" of rasters. We will artificially add NA rows and columns to
# one raster to demonstrate how the trim() function removes only rows/columns
# that are NA for *all* rasters.
elevNAs <- elev

fun <- " = if(col() > ncols() - 200, null(), madElev)"
elevNAs <- app(elevNAs, fun)

# Notice raster is "narrower" because we added NA columns
plot(elevNAs)

elevs <- c(elev, elevNAs)
trimmedElevs <- trim(elevs)
trimmedElevNAs <- trim(elevNAs)

dim(elevs)
dim(trimmedElevNAs)
dim(trimmedElevs)

}

adamlilith/fasterRaster documentation built on Dec. 21, 2024, 2:04 a.m.