LakeAcidity               package:gss               R Documentation

_W_a_t_e_r _A_c_i_d_i_t_y _i_n _L_a_k_e_s

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

     Data extracted from the Eastern Lake Survey of 1984 conducted by
     the United States Environmental Protection Agency, concerning 112
     lakes in the Blue Ridge.

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

     data(LakeAcidity)

_F_o_r_m_a_t:

     A list containing 112 observations on the following variables.

       `ph'    Surface ph.
       `cal'   Calcium concentration.
       `lat'   Latitude.
       `lon'   Longitude.
       `geog'  Geographic location, derived from `lat' and `lon'

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

     `geog' was generated from `lat' and `lon' using the code given in
     the Example section.

_S_o_u_r_c_e:

     Douglas, A. and Delampady, M. (1990), Eastern Lake Survey - Phase
     I: Documentation for the Data Base and the Derived Data sets. Tech
     Report 160 (SIMS), Dept. Statistics, University of British
     Columbia.

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

     Gu, C. and Wahba, G. (1993), Semiparametric analysis of variance
     with tensor product thin plate splines.  Journal of the Royal
     Statistical Society Ser. B, 55, 353-368.

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

     ## Converting latitude and longitude to x-y coordinates
     convert <- function(lat, lon) {
         lat <- lat/180*pi
         lon <- lon/180*pi
         m.lat <- (max(lat)+min(lat))/2
         m.lon <- (max(lon)+min(lon))/2
         x <- cos(m.lat)*sin(m.lon-lon)
         y <- sin(lat-m.lat)
         cbind(x,y)
     }
     convert(LakeAcidity$lat,LakeAcidity$lon)

