gridweights             package:spatstat             R Documentation

_C_o_m_p_u_t_e _Q_u_a_d_r_a_t_u_r_e _W_e_i_g_h_t_s _B_a_s_e_d _o_n _G_r_i_d _C_o_u_n_t_s

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

     Computes quadrature weights for a given set of points, using the
     ``counting weights'' for a grid of rectangular tiles.

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

      gridweights(X, nx, ny, window=NULL)

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

       X: Data defining a point pattern.

      nx: Number of tiles in each row of the rectangular grid. 

      ny: Number of tiles in each column of the rectangular grid. 

  window: Default window for the point pattern

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

     This function computes a set of quadrature weights for a given
     pattern of points (typically comprising both ``data'' and `dummy''
     points). See `quad.object' for an explanation of quadrature
     weights and quadrature schemes.

     The weights are computed by the ``counting weights'' rule based on
     a regular grid of rectangular tiles. First `X' and (optionally)
     `window' are converted into a point pattern object. Then the
     bounding rectangle of the window of the point pattern is divided
     into a regular nx * ny grid of rectangular tiles. The weight
     attached to a point of `X' is the area of the tile in which it
     lies, divided by the number of points of `X' lying in that tile.

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

     Vector of nonnegative weights for each point in `X'.

_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', `dirichlet.weights'

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


       library(spatstat)

       Q <- quadscheme(runifpoispp(10))
       X <- as.ppp(Q) # data and dummy points together
       w <- gridweights(X, 10, 10)

