Reclassifies a raster .tif layer based on a look-up table, such that the output raster contains the new values. The function uses the r.reclass function of GRASS GIS.
Note that the input raster needs to be of type integer. If the input raster layer has floating point values, you can multiply it by some factor (e.g. 1000) to achieve integer values, otherwise the GRASS GIS r.reclass will round the raster values down to the next integer which is not always desired.
Usage
reclass_raster(
data,
rast_val,
new_val,
raster_layer,
recl_layer,
no_data = -9999,
type = "Int32",
compression = "low",
bigtiff = TRUE,
read = FALSE,
quiet = TRUE
)Arguments
- data
a data.frame or data.table with the original and new values to be written to the raster.
- rast_val
character. The name of the column with the original raster values.
- new_val
character. The name of the column with the new raster values, which need to be integer values. In case of floating point values, consider multiplying the values e.g. by 1000 to keep three decimals.
- raster_layer
Full path to the input raster .tif layer.
- recl_layer
character. Full path of the output .tif layer, i.e., the reclassified raster file.
- no_data
numeric. The no_data value of the new .tif layer. Default is -9999.
- type
character. Data type; Options are Byte, Int16, UInt16, Int32, UInt32,CInt16, CInt32. Default is Int32. Note that only integer values are allowed.
- compression
character. Compression of the written output file. Compression levels can be defined as "none", "low", or "high". Default is "low", referring to compression type "DEFLATE" and compression level 2. "high" refers to compression level 9.
- bigtiff
logical. Define whether the output file is expected to be a BIGTIFF (file size larger than 4 GB). If FALSE and size > 4GB no file will be written. Default is TRUE.
- read
logical. If TRUE, then the reclassified raster .tif layer gets read into R as a SpatRaster (terra object). If FALSE, the layer is only stored on disk. Default is FALSE.
- quiet
logical. If FALSE, the standard output will be printed. Default is TRUE.
Examples
# Download test data into the temporary R folder
# or define a different directory
my_directory <- tempdir()
download_test_data(my_directory)
# Read the stream order for each sub-catchment as a data.table
my_dt <- read_geopackage(gpkg= paste0(my_directory,
"/hydrography90m_test_data",
"/order_vect_59.gpkg"),
import_as = "data.table")
# Select the stream segment ID and and the Strahler stream order
str_ord <- my_dt[,c("stream", "strahler")]
# Define input and output raster layer
stream_raster <- paste0(my_directory,
"/hydrography90m_test_data/stream_1264942.tif")
recl_raster <- paste0(my_directory,
"/hydrography90m_test_data/reclassified_raster.tif")
# Reclassify the stream network to obtain the Strahler stream order raster
str_ord_rast <- reclass_raster(data = str_ord,
rast_val = "stream",
new_val = "strahler",
raster_layer = stream_raster,
recl_layer = recl_raster)