

splint(funfits)                              R Documentation

_C_u_b_i_c _s_p_l_i_n_e _i_n_t_e_r_p_o_l_a_t_i_o_n

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

     Fits a piecewise cubic polynomial to the x and y values
     assuming that the second and third derivatives are zero
     at the range of the x values. For this reason extrapo-
     lation outside the range of the x values will be a lin-
     ear function.

_U_s_a_g_e_:

     splint(x, y, xgrid, derivative=0)

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

       x: The x values the define the curve or a two column
          matrix of x and y values.

       y: The y values that are paired with the x's.

   xgrid: The grid to evaluate the fitted cubic interpolat-
          ing curve.

derivative: Indicates whether the function or a a first or
          second derivative should be evaluated.

_V_a_l_u_e_:

     A vector consisting of the spline evaluated at the grid
     values.

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

     See Additive Models by Hastie and Tibshriani.

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

     spreg, sreg, tps

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

     splint(ozone$x[,1],ozone$y,seq(min(ozone$x[,1]),max(ozone$x[,1]),,40)) -> fit
     # evaluate cubic spline to ozone at longitude values on grid of
     # longitude values

