grtspts               package:spsurvey               R Documentation

_S_e_l_e_c_t _G_R_T_S _S_a_m_p_l_e _o_f _a _F_i_n_i_t_e _R_e_s_o_u_r_c_e

_D_e_s_c_r_i_p_t_i_o_n:

     This function select a GRTS sample of a finite 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.

_U_s_a_g_e:

     grtspts(src.frame="shapefile", shapefilename=NULL, ptsframe, samplesize=100,
        SiteBegin=1, shift.grid=TRUE, do.sample=TRUE, startlev=NULL, maxlev=11) 

_A_r_g_u_m_e_n_t_s:

src.frame: source of the frame, which equals "shapefile" if the frame
          is to be read from a shapefile, or "att.frame" if the frame
          is included in ptsframe.  The default is "shapefile".

shapefilename: name of the input shapefile.  If src.frame equal
          "shapefile" and shapefilename equals NULL, then the shapefile
          or shapefiles in the currrent directory are used.  The
          default is NULL.

ptsframe: a data frame containing id, x, y, 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.

do.sample: option to select a sample, where TRUE means select a sample 
          and FALSE means return the entire sample frame in reverse
          hierarchical  order.  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.

_V_a_l_u_e:

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

_A_u_t_h_o_r(_s):

     Tony Olsen Olsen.Tony@epa.gov
      Tom Kincaid Kincaid.Tom@epa.gov

_R_e_f_e_r_e_n_c_e_s:

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

_S_e_e _A_l_s_o:

     'grts'

