update: Update a raster file

In terra: Spatial Data Analysis

Update a raster file

Description

Update metadata or cell values of a file that is the data source of a SpatRaster. This modifies the file on disk directly without reading the entire raster into memory.

BE CAREFUL with this function as you are overwriting data in an existing file.

Usage

## S4 method for signature 'SpatRaster'
update(object, crs=FALSE, extent=FALSE, names=FALSE,
    cells=NULL, values=NULL, layer=0)

Arguments

object	SpatRaster with a file source
crs	logical. Should the coordinate reference system be updated?
extent	logical. Should the extent be updated?
names	logical. Should the names be updated?
cells	numeric. Cell numbers to update (1-indexed). Must be used together with values
values	numeric. New values for the specified cells. Can be a single value (recycled), one value per cell (applied to all layers), or length(cells) * length(layer) values (one per cell per layer, in layer-major order)
layer	numeric or character. Layer(s) to update. Use 0 (default) to update all layers. Positive integers or layer names select specific layers

Details

The cells and values arguments allow updating specific cell values on disk without loading the raster into memory. This is useful for modifying very large rasters that cannot fit in memory. See set.values for modifying values of in-memory rasters.

Value

SpatRaster (invisibly)

Examples

## update metadata
s <- rast(system.file("ex/logo.tif", package="terra"))   
fname <- paste0(tempfile(), ".tif")
x <- writeRaster(s*1, fname)

ext(x) <- ext(x) + 1
crs(x) <- "+proj=utm +zone=1"
names(x) <- LETTERS[1:3]

update(x, crs=TRUE, extent=TRUE, names=TRUE)

rast(fname)

## update cell values on disk
r <- rast(nrows=10, ncols=10, vals=1:100)
f <- paste0(tempfile(), ".tif")
x <- writeRaster(r, f)
x[c(1, 2, 50, 51, 100)]
update(x, cells=c(1, 50, 100), values=c(999, 888, 777))
rast(f)[c(1, 2, 50, 51, 100)]

## update specific layer only
r <- rast(nrows=5, ncols=5, nlyr=3, vals=1:75)
f <- paste0(tempfile(), ".tif")
x <- writeRaster(r, f, datatype="FLT4S")
x[c(1, 2, 25, 26)]
update(x, cells=c(1, 25), values=c(0, 0), layer=2)
rast(f)[c(1, 2, 25, 26)]

terra documentation built on Aug. 22, 2026, 5:07 p.m.