spsurvey (version 3.1)

grtsarea: Select GRTS Sample of an Area Resource

Description

This function select a GRTS sample of an area resource. This function uses hierarchical randomization to ensure that the sample will include no more than one point per cell and then picks a point in selected cells.

Usage

grtsarea(shapefilename=NULL, areaframe, samplesize=100, SiteBegin=1, shift.grid=TRUE, startlev=NULL, maxlev=11, maxtry=1000)

Arguments

shapefilename

name of the input shapefile. If shapefilename equals NULL, then the shapefile or shapefiles in the working directory are used. The default is NULL.

areaframe

a data frame containing id, mdcaty and mdm.

samplesize

number of points to select in the sample. The default is 100.

SiteBegin

number to use for first site in the design. The default is 1.

shift.grid

option to randomly shift the hierarchical grid, where TRUE means shift the grid and FALSE means do not shift the grid, which is useful if one desires strict spatial stratification by hierarchical grid cells. The default is TRUE.

startlev

initial number of hierarchical levels to use for the GRTS grid, which must be less than or equal to maxlev (if maxlev is specified) and cannot be greater than 11. The default is NULL.

maxlev

maximum number of hierarchical levels to use for the GRTS grid, which cannot be greater than 11. The default is 11.

maxtry

maximum number of iterations for randomly generating a point The default is 1000.

Value

A data frame of GRTS sample points containing: SiteID, id, x, y, mdcaty, and weight.

References

Stevens, D.L., Jr., and A.R. Olsen. (2004). Spatially-balanced sampling of natural resources. Journal of the American Statistical Association 99, 262-278.

See Also

grts