We have been asked multiple times how we are “dealing with the transition from raster to terra”. The answer is, somewhat painfully and more slowly than we had hoped for.
Much of what we do involves manipulating spatial objects (raster or vector data) be it for data extraction (e.g., extracting data for statistical modelling), results production (e.g., outputting results spatially) or visualisation (e.g., making maps) and our packages and SpaDES modules were deeply intertwined with the raster and sp packages.
We have started the transition more than a year ago and still haven’t finished. Part of the reason why this takes so long is because we are attempting to keep backwards compatibility. Which take us to the purpose of this post.
Our advice to others in the same transition journey as us:
That’s all really.
Below is a lit of raster to terra (or other packages) function equivalencies that may be useful. Note that these are likely to change as terra and other packages evolve.
See also the description of terra methods for more useful information.
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raster package
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terra or other packages
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ras[]
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as.vec t o r(ras[])as.vector(values(ras))
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compareCRS
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For now,
LandR::.compareCRS – only 2 rasters
LandR::.compareRas – multiple rasters
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maxValue, minValue
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minmax or
reproducible::minFn, reproducible::maxFn
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compareRaster
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terra::compareGeom – more sensitive than st_crs(x) == st_crs(y) and returns false negatives in many situations.
Alternatives are:
sf::st_crs(x) == s f::st_crs(y)LandR::.compareRas
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getValues
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SpatRaster[] returns a matrix, even if it is just one layer; RasterLayer[] returns a vector; RasterStack[] returns a matrix
For consistency, use:
reproducible::values2
which replicates the old RasterLayer/RasterStack behaviour of vector if 1 layer, matrix if > 1 layer, using internally:
terra:: v a lues(ras, mat = nlyr(ras) > 1) if ras is a RasterLayer
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setValues
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ras[] <-
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extract, mask, ncell, cover
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Same function names in terra, all compatible with RasterLayer and RasterStack
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raster(ras)
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Used to create a template raster.
terra equivalent is:
rast(ras)
reproducible::rasterRead can use either, depending on value of getO p t ion(“reproducible.rasterRead”)
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raster(filepath)
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Used to load a raster from a file.
terra equivalent is rast(filepath)
reproducible::rasterRead can use either, depending on value of getO p t ion(“reproducible.rasterRead”)
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layerNames
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names
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extent
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terra::ext – compatible with RasterLayer and RasterStack
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res
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terra::res – compatible with RasterLayer and RasterStack
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nlayers
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length(names(ras)) or terra::nlyr; new transition function reproducible::nlayers2 works with either RasterLayer or SpatRaster
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as.integer(ras) doesn’t work for SpatRaster … this also doesn’t work:
ras[] <- as.integer(ras[])
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ras <- LandR::asInt(ras) works on RasterLayer or SpatRaster
LandR::isInt # the equivalent for is.integer
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setColors
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See terra::coltab
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subs
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terra::subst – but arguments are different
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fasterize::fasterize
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No equivalent for SpatVector objects yet.
Use terra::rasterize but this appears to be slow at the moment. sf objects may need to be converted to a temporary SpatVector
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SpaDES.core::Plots(ras)
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Use
SpaDES.core::Plo t s (ras, fn = LandR::plotRast, …) available in LandRdevelopment
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quickPlot::Plot(ras)
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quickPlot::Plot(ras) – accepts SpatRaster
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raster::dataType
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Equivalent in terra is datatype (notice different capitalization)
reproducible::dataType2 works on RasterLayer and SpatRaster
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xyFromCell
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terra::xyFromCell(…, cell) does not accept (unlike r aster::xyFromCell(…, cell))
Passing as.vector(cell) will work with RasterLayer and SpatRaster
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clump()
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patches()
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filename()
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Equivalent in terra is sources()
reproducible::Filenames() works on either RasterLayer or SpatRaster
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