

_M_o_n_o_t_o_n_e _I_n_v_e_r_s_e _S_p_l_i_n_e

     backSpline(object)

_A_r_g_u_m_e_n_t_s:

  object: An object that inherits from class `nbSpline' or
          `npolySpline'.  That is, the object must represent
          a natural interpolation spline but it can be
          either in the B-spline representation or the
          piecewise polynomial representation. The spline is
          checked to see if represents a monotone function.

_D_e_s_c_r_i_p_t_i_o_n:

     Create a monotone inverse of a monotone natural spline.

_V_a_l_u_e:

     An object of class `polySpline' that contains the
     piecewise polynomial representation of a function that
     has the appropriate values and derivatives at the knot
     positions to be an inverse of the spline represented by
     `object'.  Technically this object is not a spline
     because the second derivative is not constrained to be
     continuous at the knot positions.  However, it is often
     a much better approximation to the inverse than fitting
     an interpolation spline to the y/x pairs.

_A_u_t_h_o_r(_s):

     Douglas Bates and Bill Venables

_S_e_e _A_l_s_o:

     `interpSpline'

_E_x_a_m_p_l_e_s:

     data( women )
     ispl <- interpSpline( women$height, women$weight )
     bspl <- backSpline( ispl )
     plot( bspl )    # plots over the range of the knots

