srs.polygon: Draws a Simple Random Sample (SRS) from an area resource...

In semmons1/TEST-SDraw: Spatially Balanced Samples of Spatial Objects

Description

Draws a simple random sample from a SpatialPolygons or SpatialPolygonsDataFrame object.

Usage

srs.polygon(x, n)

Arguments

x	A SpatialPolygons or SpatialPolygonsDataFrame object. This object must contain at least 1 polygon. If it contains more than 1 polygon, the SRS sample is drawn from the union of all polygons. Holes are respected.
n	Sample size. Number of locations to draw from the union of all polygons contained in x.

Details

The SRS sample is drawn by generating uniform random deviates for coordinates in the bounding box surrounding polygons (e.g., c(xmin, ymin) + c(dx,dy)*runif(2)), tossing locations outside polygons until the required number is achieved.

Value

A SpatialPointsDataFrame containing locations in the SRS sample, in arbitrary order. Attributes of the sample points (in the embedded data frame) are as follows:

• sampleID: A unique identifier for every sample point.

• geometryID: The ID of the polygon in x which each sample point falls. The ID of polygons in x are row.names(geometry(x)).

• Any attributes of the original polygons (in x).

Additional attributes of the output object, beyond those which make it a SpatialPointsDataFrame, are:

• frame: Name of the input sampling frame.

• frame.type: Type of resource in sampling frame. (i.e., "polygon").

• sample.type: Type of sample drawn. (i.e., "SRS").

Author(s)

Trent McDonald

See Also

bas.polygon, sss.polygon, hip.polygon, sdraw

Examples

# A square grid oriented east-west
WA.samp <- srs.polygon( WA, 100 )   
plot( WA )
points( WA.samp, pch=16 )

semmons1/TEST-SDraw documentation built on June 8, 2019, 9:33 a.m.