2 Working with Data
This section covers changes made to common data manipulation and querying methods.
2.1 Renamed Methods
In general, when method names were changed in terra, they got shorter and more similar to base R. Most capital letters were removed as well.
| Old Methods | New Method |
|---|---|
| coordinates | crds |
| getValues | values |
| nlayers | nlyr |
| reclassify, subs, cut | classify |
| stack, addLayer | c |
| unstack | as.list |
| dropLayer | subset |
| rasterTo* | as.* |
| isLonLat | is.lonlat |
| bind | rbind |
2.2 Combined Methods
Many tasks that previously at separate methods for raster and vector data, due to the classes originating in separate packages, now have shared method names. Functions in green rows have been renamed, while functions in grey rows, maintain their name from raster.
| Operation | Old Methods | New Method |
|---|---|---|
| reproject geometry | projectRaster, sp::spTransform | project |
| combine cells/polygons | aggregate | aggregate |
| split cells/polygons | disaggregate | disagg |
| spatial query | extract, sp::over | extract |
| spatial sampling | sp::spsample, sampleRandom | spatSample |
2.3 Speed Improvements
Many of the most time-intensive operations got speed boosts from the C++ implementation.
| function | median (millisec) | n_eval |
|---|---|---|
| terra::spatSample | 1.98 | 100 |
| raster::sampleRandom | 6.28 | 100 |
| terra::project | 34.17 | 100 |
| raster::projectRaster | 57.14 | 100 |
| terra::resample | 1.79 | 100 |
| raster::resample | 51.62 | 100 |
| terra::rasterize | 1.69 | 100 |
| raster::rasterize | 236.27 | 100 |
| terra::as.polygons | 27.35 | 100 |
| raster::rasterToPolygons | 210.74 | 100 |
2.4 Spatial Relationships
A key function in any GIS software is the ability to determine the
relationship between two spatial objects. Previous packages (raster,
rgeos) used used different method names depending on the geometric query
in question. Rgeos in particular contained at least twelve functions
just for determining spatial relationship. In terra, the number of
objects compared (not the relationship type) determines the function
used. For one-to-one and one-to-many comparisons use is.related(), for
many-to-many comparisons, use relate(). The relation argument
specifies relationship type. Options include intersects, touches,
crosses, overlaps, within, contains, covers, covered by, disjoint, or
DE-9IM strings.
## [1] TRUEMethod names for the spatial operations below remain unchanged:
union()intersect()symdif()buffer()crop()cover()mask()