Draw a systematic sample from a
SpatialPoints* object or a
SpatialPoints* objects can represent point resources in 2-dimensional space, such as towns, event locations,
or grid cell centers.
Sample size. Number of points or rows to draw from
x is a data frame, the simple random sample is drawn from the rows. That is,
each row is viewed as a sample unit.
This draws equi-probable sample. First order inclusion probabilities are n/N for all units.
x inherits from a the
SpatialPoints class, a
SpatialPointsDataFrame object containing locations and attributes in the sample is returned.
x is a
data.frame is returned.
Attributes of the returned sample points are:
sampleID: A unique identifier for every sample point.
sampleID starts with 1 at the first point and
increments by one for each.
x inherits from
returned points have attribute
geometryID – the ID (=
the sampled point.
Any attributes (columns) associated with the input points (rows).
Additional attributes of the output object are:
frame: Name of the input sampling frame (i.e.,
frame.type: Type of resource in sampling frame. (i.e., "point").
sample.type: Type of sample drawn. (i.e., "SRS").
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