strata | R Documentation |
Stratification units are created from the spatial intersection of raster layers representing different sets of classification units. Each set of classification units is related to a particular landscape factor (e.g., topography, climate) or to a particular spatial scale for a single landscape factor (e.g., micro-climate, macro-topography). Each resulting stratification unit is considered to represent a distinct landscape configuration in terms of multiple landscape factors/factor scales (represented by the classification units). This function automatically assigns a unique numeric code to each stratification unit. For x stratification unit, the numeric code represents the unique combination of classification units whose spatial intersection resulted in x. See Examples to get a better idea of the logic behind the code assignment process.
strata(cu.rast, to.disk = FALSE, outdir = ".", su.name, ...)
cu.rast |
SpatRaster, as in |
to.disk |
Boolean. Write the resulting raster layer of stratification units to disk? Default: FALSE |
outdir |
Character. If to.disk = TRUE, string specifying the path for the output raster layer of stratification units. Default: "." |
su.name |
Character. If to.disk = TRUE, file name (including extension) for the output raster layer of stratification units. |
... |
Additional arguments as for |
When printing su.rast$code.mult, the output shows the multiplier used for each landscape factor/factor scale. From this output, one can manually replicate the creation of stratification units through simple raster algebra. To do so, a weighted sum of the SpatRasters containing the classification units for each landscape factor/factor scale should be performed using the multipliers as weights. Note that the weights do not imply relative importance. The weights are required only to preserve a logical structure of the landscape factors/factor scales in the resulting numeric code.
su.rast: Single-layer SpatRaster representing the stratification units occurring across geographic space. The cell values in this raster layer represents the numeric codes of stratification units.
code.mult: Multipliers used for the creation of the numeric codes. See Details.
Other Functions for Landscape Stratification:
som_gap()
,
som_pam()
require(terra) p <- system.file("exdat", package = "rassta") # Multi-layer SpatRast with classification units (Cus) ## Three sets (i.e., landscape factors): geology, climate and topography fcu <- list.files(path = p, pattern = "geology.tif|climate.tif|topography.tif", full.names = TRUE ) cu <- terra::rast(fcu) # Stratification units (SUs) su <- strata(cu.rast = cu) # Plot the stratification units if(interactive()){plot(su$su.rast, type = "classes")} # # Note code structure from SUs and corresponding values from CUs z <- c(su$su.rast, cu)[46,61] # Example of one cell (row = 45, column = 45) su$code.mult # Multipliers z[c("SU", names(su$code.mult))] # Code structure # Note what happens when some landscape factors have cell values greater... #... than 1 digit (i.e., more than 9 distinct classification units) cu <- c(cu[[1]], cu[[2]]^4, cu[[3]]^2) su <- strata(cu.rast = cu) su$code.mult c(su$su.rast, cu[[names(su$code.mult)]])[46,61]
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