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Set the variable name of a SpatRaster within a pipe

Source: R/spat_set_raster_varnames.R
set_raster_varnames.Rd

A small wrapper function that assigns a single variable name varnames to a SpatRaster and returns the object, making it suitable for use in a magrittr pipe without breaking the chain.

Usage

set_raster_varnames(rast, var_name)

Arguments

rast

[SpatRaster] A SpatRaster object whose variable name is to be set. Must not be NULL.

var_name

[character(1)] or NULL. A single non-empty string to assign as the variable name. If NULL, the variable name is reset to "" (terra's default empty state).

Value

The input SpatRaster with an updated varnames slot.

names vs varnames

terra stores two distinct name slots:

  • names (per-layer) – used in plots, as.data.frame(), and subsetting. Set via names(x) <- ... or terra::set.names().

  • varnames (per-data-source) – a single string inherited from the source file variable name (e.g. NetCDF). For any in-memory or derived SpatRaster there is always exactly one data source regardless of the number of layers, so varnames only ever holds one value.

Author

Ahmed El-Gabbas

Examples

library(terra)

r <- terra::rast(
  ncols = 10, nrows = 10, nlyr = 3, vals = 1L, names = c("l1", "l2", "l3"))

# setting variable names directly with terra
terra::varnames(r) <- "v1"
r
#> class       : SpatRaster
#> size        : 10, 10, 3  (nrow, ncol, nlyr)
#> resolution  : 36, 18  (x, y)
#> extent      : -180, 180, -90, 90  (xmin, xmax, ymin, ymax)
#> coord. ref. : lon/lat WGS 84 (CRS84) (OGC:CRS84)
#> source      : spat_20fe8f55571_8446_BnO3HOrWuPceBcV.tif
#> varname     : v1
#> names       : l1, l2, l3
#> min values  :  1,  1,  1
#> max values  :  1,  1,  1

# Set variable name within a pipe
(r2 <- set_raster_varnames(r, "temperature"))
#> class       : SpatRaster
#> size        : 10, 10, 3  (nrow, ncol, nlyr)
#> resolution  : 36, 18  (x, y)
#> extent      : -180, 180, -90, 90  (xmin, xmax, ymin, ymax)
#> coord. ref. : lon/lat WGS 84 (CRS84) (OGC:CRS84)
#> source      : spat_20fe8f55571_8446_BnO3HOrWuPceBcV.tif
#> varname     : temperature
#> names       : l1, l2, l3
#> min values  :  1,  1,  1
#> max values  :  1,  1,  1

# Reset variable name to empty
(r3 <- set_raster_varnames(r, NULL))
#> class       : SpatRaster
#> size        : 10, 10, 3  (nrow, ncol, nlyr)
#> resolution  : 36, 18  (x, y)
#> extent      : -180, 180, -90, 90  (xmin, xmax, ymin, ymax)
#> coord. ref. : lon/lat WGS 84 (CRS84) (OGC:CRS84)
#> source      : spat_20fe8f55571_8446_BnO3HOrWuPceBcV.tif
#> names       : l1, l2, l3
#> min values  :  1,  1,  1
#> max values  :  1,  1,  1