Variogram.corExp            package:nlme            R Documentation

_C_a_l_c_u_l_a_t_e _S_e_m_i-_v_a_r_i_o_g_r_a_m _f_o_r _a _c_o_r_E_x_p _O_b_j_e_c_t

_D_e_s_c_r_i_p_t_i_o_n:

     This method function calculates the semi-variogram values
     corresponding to the Exponential correlation model, using the
     estimated coefficients corresponding to 'object', at the distances
     defined by 'distance'.

_U_s_a_g_e:

     ## S3 method for class 'corExp':
     Variogram(object, distance, sig2, length.out, ...)

_A_r_g_u_m_e_n_t_s:

  object: an object inheriting from class 'corExp', representing an
          exponential spatial correlation structure.

distance: an optional numeric vector with the distances at which the
          semi-variogram is to be calculated. Defaults to 'NULL', in
          which case a sequence of length 'length.out' between the
          minimum and maximum values of 'getCovariate(object)' is used.

    sig2: an optional numeric value representing the process variance.
          Defaults to '1'.

length.out: an optional integer specifying the length of the sequence
          of distances to be used for calculating the semi-variogram,
          when 'distance = NULL'. Defaults to '50'.

     ...: some methods for this generic require additional arguments. 
          None are used in this method.

_V_a_l_u_e:

     a data frame with columns 'variog' and 'dist' representing,
     respectively, the semi-variogram values and the corresponding
     distances. The returned value inherits from class 'Variogram'.

_A_u_t_h_o_r(_s):

     Jose Pinheiro Jose.Pinheiro@pharma.novartis.com and Douglas Bates
     bates@stat.wisc.edu

_R_e_f_e_r_e_n_c_e_s:

     Cressie, N.A.C. (1993), "Statistics for Spatial Data", J. Wiley &
     Sons.

_S_e_e _A_l_s_o:

     'corExp', 'plot.Variogram', 'Variogram'

_E_x_a_m_p_l_e_s:

     stopifnot(require("stats", quietly = TRUE))
     cs1 <- corExp(3, form = ~ Time | Rat)
     cs1 <- Initialize(cs1, BodyWeight)
     Variogram(cs1)[1:10,]