

lowess {base}                                R Documentation

_S_c_a_t_t_e_r _P_l_o_t _S_m_o_o_t_h_i_n_g

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

     This function performs the computations for the LOWESS
     smoother (see the reference below).  `lowess' returns a
     list containing components `x' and `y' which give the
     coordinates of the smooth.  The smooth should be added
     to a plot of the original points with the function
     `lines'.

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

     lowess(x, y, f=2/3, iter=3, delta=.01*diff(range(x)))

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

     x,y: vectors giving the coordinates of the points in
          the scatter plot.  Alternatively a single plotting
          structure can be specified.

       f: the smoother span.  This gives the proportion of
          points in the plot which influence the smooth at
          each value.  Larger values give more smoothness.

    iter: the number of robustifying iterations which should
          be performed.  Using smaller values of `iter' will
          make `lowess' run faster.

   delta: values of `x' which lie within `delta' of each
          other replaced by a single value in the output
          from `lowess'.

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

     Cleveland, W. S. (1979).  Robust locally weighted
     regression and smoothing scatterplots.  J. Amer.
     Statist. Assoc. 74, 829-836.

     Cleveland, W. S. (1981).  LOWESS: A program for smooth-
     ing scatterplots by robust locally weighted regression.
     The American Statistician, 35, 54.

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

     data(cars)
     plot(cars, main = "lowess(cars)")
     lines(lowess(cars), col= 2)
     lines(lowess(cars,f=.2), col= 3)
     legend(5,120,c(paste("f = ", c("2/3", ".2"))), lty=1, col=2:3)

