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spsurvey (version 4.1.4)

grtsarea: Select a Generalized Random-Tesselation Stratified (GRTS) Sample of an Area Resource

Description

This function select a GRTS sample of an area resource. The 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(areaframe, samplesize = 100, SiteBegin = 1,
  shift.grid = TRUE, startlev = NULL, maxlev = 1, maxtry = NULL)

Arguments

areaframe

The sf object containing attributes: id, mdcaty and mdm.

samplesize

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

SiteBegin

First number to start siteID numbering. The default is 1.

shift.grid

Option to randomly shift the hierarchical grid. 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

This argument is depricated.

Value

Data frame of sample points containing: siteID, id, x, y, mdcaty, and weight.

Other Functions Required

numLevels

determines the number of levels for hierarchical randomization

constructAddr

constructs the hierarchical address for sample points

ranho

constructs the randomized hierarchical address for sample points

pickGridCells

selects grid cells that get a sample point

insideAreaGridCell

determines feature ID value and clipped polygon area for each feature contained in a selected grid cell

selectFeatureID

identifies a feature ID from which to select a sample point

pickSamplePoints

selects sample points from an sf object