grtslin: Select a Generalized Random-Tesselation Stratified (GRTS) Sample of a Linear Resource

Description

This function select a GRTS sample of a linear 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

grtslin(shapefilename = NULL, linframe, samplesize = 100,
  SiteBegin = 1, shift.grid = TRUE, startlev = NULL, maxlev = 1)

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.

linframe

Data frame containing 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.

Value

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

Other Functions Required

numLevels: C function to determine the number of levels for hierarchical randomization
constructAddr: C function to construct the hierarchical address for all points
ranho: C function to construct the randomized hierarchical address for all points
pickGridCells: C function to select grid cells that get a sample point
insideLinearGridCell: C function to determine ID value and clipped polyline length for shapefile records contained in the selected grid cells
selectrecordID: select a shapefile record from which to select a sample point
pickLinearSamplePoints: C function to pick sample points in the selected grid cells