nndist               package:spatstat               R Documentation

_N_e_a_r_e_s_t _n_e_i_g_h_b_o_u_r _d_i_s_t_a_n_c_e_s

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

     Computes the distance from each point to its nearest neighbour in
     a point pattern.

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

       nndist(X, ..., method="C")
       nndist.ppp(X, ..., method="C")
       nndist.default(X, Y=NULL, ..., method="C")

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

     X,Y: Arguments specifying the locations of a set of points. For
          'nndist.ppp', the argument 'X' should be a point pattern
          (object of class '"ppp"'). For 'nndist.default', typically
          'X' and 'Y' would be numeric vectors of equal length.
          Alternatively 'Y' may be omitted and 'X' may be a list with
          two components 'x' and 'y', or a matrix with two columns. 

     ...: Ignored by 'nndist.ppp' and 'nndist.default'. 

  method: String specifying which method of calculation to use. Values
          are '"C"' and '"interpreted"'. 

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

     This function computes the Euclidean distance from each point in a
     point pattern to its nearest neighbour (the nearest other point of
     the pattern).

     The function 'nndist' is generic, with a method for point patterns
     (objects of class '"ppp"') and a default method.

     The method for point patterns expects a single point pattern
     argument 'X' and returns the vector of its nearest neighbour
     distances.

     The default method expects that 'X' and 'Y' will determine the
     coordinates of a set of points. Typically 'X' and 'Y' would be
     numeric vectors of equal length. Alternatively 'Y' may be omitted
     and 'X' may be a list with two components named 'x' and 'y', or a
     matrix or data frame with two columns.

     The argument 'method' is not normally used. It is retained only
     for checking the validity of the software. If 'method =
     "interpreted"' then the distances are computed using interpreted R
     code only. If 'method="C"' (the default) then C code is used.  The
     C code is faster by two to three orders of magnitude and uses much
     less memory.

     If there is only one point (if 'x' has length 1), then a nearest
     neighbour distance of 'Inf' is returned. If there are no points
     (if 'x' has length zero) a numeric vector of length zero is
     returned.

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

     Numeric vector of the nearest neighbour distances for each point.

_W_a_r_n_i_n_g_s:

     An infinite value is returned if there is only one point in the
     point pattern.

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

     Pavel Grabarnik pavel.grabar@issp.serpukhov.su and Adrian Baddeley
     adrian@maths.uwa.edu.au <URL:
     http://www.maths.uwa.edu.au/~adrian/>

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

     'pairdist', 'Gest'

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

        data(cells)
        d <- nndist(cells)

        x <- runif(100)
        y <- runif(100)
        d <- nndist(x, y)

