spokes               package:spatstat               R Documentation

_S_p_o_k_e_s _p_a_t_t_e_r_n _o_f _d_u_m_m_y _p_o_i_n_t_s

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

     Generates a pattern of dummy points in a window, given a data
     point pattern. The dummy points lie on the radii of circles
     emanating from each data point.

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

      spokes(x, y, nrad = 3, nper = 3, fctr = 1.5)

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

       x: Vector of x coordinates of data points. 

       y: Vector of y coordinates of data points. 

    nrad: Number of radii emanating from each data point. 

    nper: Number of dummy points per radius. 

    fctr: Scale factor. Length of largest spoke radius is `fctr * M'
          where `M' is the mean nearest neighbour distance for the data
          points. 

_D_e_t_a_i_l_s:

     This function is useful in creating dummy points for quadrature
     schemes (see `quadscheme').

     Given the point pattern specified by the vectors `x' and `y', the
     function  creates a pattern of `nrad * nper * length(x)' dummy
     points.

     Around each data point `(x[i],y[i])' there are `nrad * nper' dummy
     points, lying on `nrad' radii emanating from `(x[i],y[i])', with
     `nper' dummy points equally spaced along each radius.

     The (equal) spacing of dummy points along each radius is
     controlled by the factor `fctr'.  The distance from a data point
     to the furthest of its associated dummy points is `fctr * M' where
     `M' is the mean nearest neighbour distance for the data points.

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

     A list with two components `x' and `y', which are numeric vectors
     giving the coordinates of the dummy points.

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

     Adrian Baddeley adrian@maths.uwa.edu.au <URL:
     http://www.maths.uwa.edu.au/~adrian/> and Rolf Turner
     rolf@math.unb.ca <URL: http://www.math.unb.ca/~rolf>

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

     `quad.object', `quadscheme', `inside.owin', `gridcentres',
     `stratrand'

_E_x_a_m_p_l_e_s:


       library(spatstat)

       dat <- runifrect(10)

       plot(dat)

       dum <- spokes(dat$x, dat$y)

       points(dum$x, dum$y, pch=".")

       Q <- quadscheme(dat, dum)

