droplinks               package:spdep               R Documentation

_D_r_o_p _l_i_n_k_s _i_n _a _n_e_i_g_h_b_o_u_r_s _l_i_s_t

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

     Drops links to and from or just to a region from a neighbours
     list. The example corresponds to Fingleton's Table 1, p. 6, for
     lattices 5 to 19.

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

     droplinks(nb, drop, sym=TRUE)

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

      nb: a neighbours list object of class 'nb'

    drop: either a logical vector the length of 'nb', or a character
          vector of named regions corresponding to 'nb''s region.id
          attribute, or an integer vector of region numbers

     sym: TRUE for removal of both "row" and "column" links, FALSE for
          only "row" links

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

     The function returns an object of class 'nb' with a list of
     integer vectors containing neighbour region number ids.

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

     Roger Bivand Roger.Bivand@nhh.no

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

     B. Fingleton (1999) Spurious spatial regression: some Monte Carlo
     results with a spatial unit root and spatial cointegration,
     Journal of Regional Science 39, pp. 1-19.

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

     'is.symmetric.nb'

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

     rho <- c(0.2, 0.5, 0.95, 0.999, 1.0)
     ns <- c(5, 7, 9, 11, 13, 15, 17, 19)
     mns <- matrix(0, nrow=length(ns), ncol=length(rho))
     rownames(mns) <- ns
     colnames(mns) <- rho
     mxs <- matrix(0, nrow=length(ns), ncol=length(rho))
     rownames(mxs) <- ns
     colnames(mxs) <- rho
     for (i in 1:length(ns)) {
       nblist <- cell2nb(ns[i], ns[i])
       nbdropped <- droplinks(nblist, ((ns[i]*ns[i])+1)/2, sym=FALSE)
       listw <- nb2listw(nbdropped, style="W", zero.policy=TRUE)
       wmat <- listw2mat(listw)
       for (j in 1:length(rho)) {
         mat <- diag(ns[i]*ns[i]) - rho[j] * wmat
         res <- diag(solve(t(mat) %*% mat))
         mns[i,j] <- mean(res)
         mxs[i,j] <- max(res)
       }
     }
     print(mns)
     print(mxs)

