Select an independent random sample from a point, linear, or areal frame. Frame elements must be located in 1- or 2-dimensional coordinate system. May designate panels of sites for surveys over time.
irs(design, DesignID = "Site", SiteBegin = 1, type.frame = "finite",
src.frame = "shapefile", in.shape = NULL, sp.object = NULL,
att.frame = NULL, id = NULL, xcoord = NULL, ycoord = NULL,
stratum = NULL, mdcaty = NULL, maxtry = 1000, shapefile = TRUE,
prjfilename = NULL, out.shape = "sample")Named list of stratum design specifications which are also lists. Stratum names must be subset of values in stratum argument. Each stratum list has four components:
named vector of sample sizes for each panel in stratum
the type of random selection, which must be one of following: "Equal" - equal probability selection, "Unequal" - unequal probability selection by the categories specified in caty.n and mdcaty, or "Continuous" - unequal probability selection proportional to auxiliary variable mdcaty
if seltype equals "Unequal", a named vector of sample sizes for each category specified by mdcaty, where sum of the sample sizes must equal sum of the panel sample sizes, and names must be a subset of values in mdcaty
number of replacement sites ("oversample" sites) for the entire design, which is set equal to 0 if none are required)
Example design for a stratified sample: design=list( Stratum1=list(panel=c(PanelOne=50), seltype="Equal", over=10), Stratum2=list(panel=c(PanelOne=50, PanelTwo=50), seltype="Unequal", caty.n=c(CatyOne=25, CatyTwo=25, CatyThree=25, CatyFour=25), over=75)) Example design for an unstratified sample: design <- list( None=list(panel=c(Panel1=50, Panel2=100, Panel3=50), seltype="Unequal", caty.n=c("Caty 1"=50, "Caty 2"=25, "Caty 3"=25, "Caty 4"=25, "Caty 5"=75), over=100))
Name for the design, which is used to create a site ID for each site. The default is "Site".
Number to use for first site in the design. The default is 1.
The type of frame, which must be one of following: "finite", "linear", or "area". The default is "finite".
Source of the frame, which equals "shapefile" if the frame is to be read from a shapefile, "sp.object" if the frame is obtained from an sp package object, or "att.frame" if type.frame equals "finite" and the frame is included in att.frame. The default is "shapefile".
Name (without any extension) of the input shapefile. If src.frame equal "shapefile" and in.shape equals NULL, then the shapefile or shapefiles in the working directory are used. The default is NULL.
Name of the sp package object when src.frame equals "sp.object". The default is NULL.
Data frame composed of attributes associated with elements in the frame, which must contain the columns used for stratum and mdcaty (if required). If src.frame equals "shapefile" and att.frame equals NULL, then att.frame is created from the dbf file(s) in the working directory. If src.frame equals "att.frame", then att.frame includes columns that contain x-coordinates and y-coordinates for each element in the frame. The default is NULL.
Character string containing the name of the column from att.frame that identifies the ID value for each element in the frame. If id equals NULL, a column named "id" that contains values from one through the number of rows in att.frame is added to att.frame. The default is NULL.
Character string containing the name of the column from att.frame that identifies x-coordinates when src.frame equals "att.frame". If xcoord equals NULL, then xcoord is given the value "x". The default is NULL.
Character string containing the name of the column from att.frame that identifies y-coordinates when src.frame equals "att.frame". If ycoord equals NULL, then ycoord is given the value "y". The default is NULL.
Character string containing the name of the column from att.frame that identifies stratum membership for each element in the frame. If stratum equals NULL, the design is unstratified, and a column named "stratum" (with all of its elements equal to the stratum name specified in design) is added to att.frame. The default is NULL.
Character string containing the name of the column from att.frame that identifies the unequal probability category for each element in the frame. The default is NULL.
Maximum number of iterations for randomly generating a point within the frame to select a site when type.frame equals "area". The default is 1000.
Option to create a shapefile containing the survey design information, where TRUE equals create a shapefile and FALSE equals do not create a shapefile. The default is TRUE.
Name (without any extension) of the project file for an input shapefile. The default is NULL.
Name (without any extension) of the output shapefile containing the survey design information. The default is "sample".
An object of class SpatialDesign containing the survey design information and any additional attribute variables that were provided. Optionally, a shapefile can be created that contains the survey design information.
getRecordShapeSizesC function to read the shp file of a line or polygon shapefile and return the length or area for each record in the shapefile
irsareaselect an IRS sample of an area resource
irslinselect an IRS sample of a linear resource
irsptsselect an IRS sample of a finite resource
read.dbffunction to read the dbf file of a shapefile and return a data frame containing contents of the file
readShapeFilePtsC function to read the shp file of a point shapefile and return a data frame containing the x-coordinates and y-coordinates for elements in the frame
SpatialPointssp package function to create an object of class SpatialPoints
SpatialPointsDataFramesp package function to create an object of class SpatialPointsDataFrame
writeShapeFilePointC function to create a shapefile containing the survey design information
# NOT RUN {
test.design <- list(
Stratum1=list(panel=c(PanelOne=50), seltype="Equal", over=10),
Stratum2=list(panel=c(PanelOne=50, PanelTwo=50), seltype="Unequal",
caty.n=c(CatyOne=25, CatyTwo=25, CatyThree=25, CatyFour=25), over=75))
test.attframe <- read.dbf("test.shapefile")
test.sample <- grts(design=test.design, DesignID="Test.Site",
type.frame="area", src.frame="shapefile", in.shape="test.shapefile",
att.frame=test.attframe, stratum="test.stratum", mdcaty="test.mdcaty",
shapefile=TRUE, out.shape="test.sample")
# }
# NOT RUN {
# }
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