

   QQuuaannttiillee--QQuuaannttiillee PPlloottss

        qqnorm(y, ylim, main = "Normal Q-Q Plot", xlab = "Theoretical Quantiles",
               ylab = "Sample Quantiles", plot.it = TRUE, ...)
        qqline(y, ...)
        qqplot(x, y, plot.it = TRUE, xlab = deparse(substitute(x)),
               ylab = deparse(substitute(y)), ...)

   AArrgguummeennttss::

          x: The first sample for `qqplot'.

          y: The second or only data sample.

   DDeessccrriippttiioonn::

        `qqnorm' produces a normal QQ plot of the values in
        `y'.  `qqline' adds a line to a normal quantile-quan-
        tile plot which passes through the first and third
        quartiles.

        `qqplot' produces a QQ plot of two datasets.

        Graphical parameters may be given as arguments to
        `qqnorm', `qqplot' and `qqline'.

   VVaalluuee::

        For `qqnorm' and `qqplot', a list with components

          x: The x coordinates of the points that were/would be
             plotted

          y: The corresponding y coordinates

   SSeeee AAllssoo::

        `ppoints'.

   EExxaammpplleess::

        y <- rt(200, df = 5)
        qqnorm(y); qqline(y, col = 2)
        qqplot(y, rt(300, df = 5))
        data(precip)
        qqnorm(precip, ylab = "Precipitation [in/yr] for 70 US cities")

