splint                package: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 extrapolation outside the range of the x
     values will be a linear 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 interpolating 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

