Draw samples (point locations) from SpatialPoints, SpatialLines,
SpatialPolygons, and the *DataFrame varieties of each.
# S3 method for SpatialLines
sdraw(x, n, type, ...)# S3 method for SpatialPoints
sdraw(x, n, type, ...)
# S3 method for SpatialPolygons
sdraw(x, n, type, ...)
sdraw(x, n, type = "BAS", ...)
A spatial object. Methods are implemented for SpatialPoints,
SpatialPoints DataFrame, SpatialLines, SpatialLinesDataFrame,
SpatialPolygons, and
Spatial PolygonsDataFrame objects.
Desired sample size. Some type's of samples are fixed-size (see DETAILS),
in which case
exactly n points are returned. Other type's are variable-size,
and this number is the expected sample size (i.e., average over many repetitions).
Character, naming the type of sample to draw. Valid type's are:
"BAS" : Balanced Acceptance Sampling (Robertson et al., 2013)
"SSS" : Simple Systematic (grid) Sampling, with random start and orientation
"GRTS" : Generalized Random Tessellation Stratified sampling
(Stevens and Olsen, 2004)
"SRS" : Simple Random Sampling
"HIP" : Halton Iterative Partitioning (Robertson et al., 2017)
Optional arguments passed to underlying sample type method. See DETAILS.
A SpatialPointsDataFrame object. At a minimum, the data frame
embedded in the SpatialPoints object contains a column named siteID which
numbers the points, and geometryID which contains the ID of the
spatial object from which the point was drawn.
If x is a Spatial*DataFrame, the return's data
frame contains all attributes of x evaluated at the locations of the sample points.
Certain sampling routine add attributes
that are pertinent to the design. For example, the grts.* routines add
a pointType attribute. See documentation for the underlying sampling routine
to interpret extra output point attributes.
This is a S4 generic method for types SpatialPoints*, SpatialLines*,
and SpatialPolygons* objects.
BAS, GRTS, SRS, HIP are fixed-size designs (return exactly n points).
The SSS algorithm applied to Line and Point is fixed-sized. The SSS method
applied to Polygon frames is variable-sized.
Options which determine characteristics of each
sample time are passed via .... For example,
spacing and "shape" of the grid in sss.* are controlled via
spacing= and triangular=, while the
J parameter (which determine box sizes)
is passed to hip.*. See documentation for
hip.*, bas.*, sss.*, grts.*, and sss.*
for the full list of
parameters which determine sample characteristics.
Robertson, B.L., J. A. Brown, T. L. McDonald, and P. Jaksons (2013) "BAS: Balanced Acceptance Sampling of Natural Resources", Biometrics, v69, p. 776-784.
Stevens D. L. Jr. and A. R. Olsen (2004) "Spatially Balanced Sampling of Natural Resources", Journal of the American Statistical Association, v99, p. 262-278.
bas.polygon, bas.line, bas.point,
hip.polygon, hip.point,
sss.polygon, sss.line, sss.point,
grts.polygon, grts.line, grts.point
# NOT RUN {
# }
# NOT RUN {
WA.sample <- sdraw(WA, 50, "BAS")
WA.sample <- sdraw(WA, 50, "HIP", J=c(4,3))
WA.sample <- sdraw(WA, 50, "SSS", spacing=c(1,2))
# }
# NOT RUN {
# }
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