guplot                 package:VGAM                 R Documentation

_G_u_m_b_e_l _P_l_o_t

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

     Produces a Gumbel plot, a diagnostic plot for checking whether the
     data appears to be from a Gumbel distribution.

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

     guplot(object, ...)
     guplot.default(y, main="Gumbel Plot",
         xlab="Reduced data", ylab="Observed data", type="p", ...)
     guplot.vlm(object, ...)

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

       y: A numerical vector. 'NA's etc. are not allowed.

    main: Character. Overall title for the plot. 

    xlab: Character. Title for the x axis. 

    ylab: Character. Title for the y axis. 

    type: Type of plot. The default means points are plotted. 

  object: An object that inherits class '"vlm"', usually of class
          'vglm-class' or 'vgam-class'. 

     ...: Graphical argument passed into 'plot'. See 'par' for an
          exhaustive list. The arguments 'xlim' and 'ylim' are
          particularly useful. 

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

     If Y has a Gumbel distribution then plotting the sorted values y_i
     versus the _reduced values_ r_i should appear linear. The reduced
     values are given by

                        r_i = -log(-log(p_i))

     where p_i is the ith plotting position, taken here to be
     (i-0.5)/n. Here, n is the number of observations. Curvature
     upwards/downwards may indicate a Frechet/Weibull distribution,
     respectively. Outliers may also be detected using this plot.

     The function 'guplot' is generic, and 'guplot.default' and
     'guplot.vlm' are some methods functions for Gumbel plots.

_V_a_l_u_e:

     A list is returned invisibly with the following components. 

      x : The reduced data. 

      y : The sorted y data. 

_N_o_t_e:

     The Gumbel distribution is a special case of the GEV distribution
     with shape parameter equal to zero.

_A_u_t_h_o_r(_s):

     T. W. Yee

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

     Coles, S. (2001) _An Introduction to Statistical Modeling of
     Extreme Values_. London: Springer-Verlag.

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

     'gumbel', 'egumbel', 'gev'.

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

     ## Not run: 
     guplot(rnorm(500), las=1) -> i
     names(i)
     ## End(Not run)

