Sample a raster stack by map unit polygons, at a constant density.
sampleRasterStackByMU(
mu,
mu.set,
mu.col,
raster.list,
pts.per.acre,
p = c(0, 0.05, 0.25, 0.5, 0.75, 0.95, 1),
progress = TRUE,
estimateEffectiveSampleSize = TRUE,
polygon.id = "pID"
)a SpatialPolygonsDataFrame object in a projected coordinate reference system (CRS)
character vector of map unit labels to be sampled
column name in attribute table containing map unit labels
a list containing raster names and paths, see details below
target sampling density in points per acre
percentiles for polygon area stats, e.g. c(0.05, 0.25, 0.5, 0.75, 0.95)
logical, print a progress bar while sampling?
estimate an effective sample size via Moran's I?
Column name containing unique polygon IDs; default: "pID"; calculated if missing
A list containing:
raster.samplesa data.frame containing samples from all rasters in the stack
area.statsa data.frame containing area statistics for all map units in the collection
unsampled.idsan index to rows in the original SPDF associated with polygons not sampled
raster.summarya data.frame containing information on sampled rasters
Moran_Ia data.frame containing estimates Moran's I (index of spatial autocorrelation)
This function is used by various NRCS reports that summarize or compare concepts defined by collections of polygons using raster data sampled from within each polygon, at a constant sampling density. Even though the function name includes "RasterStack", this function doesn't actually operate on the "stack" object as defined in the raster package. The collection of raster data defined in raster.list do not have to share a common coordinate reference system, grid spacing, or extent. Point samples generated from mu are automatically converted to the CRS of each raster before extracting values. The extent of each raster in raster.list must completely contain the extent of mu.