Classical Weibull distribution plot

Plots a vector using Weibull distribution scales

Usage

weibplot(x,
            plot.pos = "exp",
            shape = NULL, scale = NULL,
            labels = NULL,
            mono = TRUE,
            ...)

Arguments

x

The vector to be plotted.

plot.pos

plotting position for points: either "exp" for expected ranks or "med" for a median rank approximation (see Details below).

shape

Shape parameter for one or several Weibull lines to be plotted.

scale

Scale parameter for one or several Weibull lines to be plotted.

labels

Text to display in legend when Weibull lines are specified.

mono

Monochrome graph.

...

Arguments to be passed to plot.

Details

This plot shows \(\log\{-\log[1-F(x)]\}\) against \(\log(x)\) where \(F(x)\) at point \(i\) is taken as \(i/(n+1)\) if plot.pos is "exp", or as the "median rank" approximation \((i-0.3)/(n+0.4)\) if plot.pos is "med".

Author

Yves Deville

Note

The graph displayed uses a log scale for x. The log-log scale for y is emulated via the construction of suitable graduations. So be careful when adding graphical material (points, etc) to this graph with functions of the "add to plot" family (points, lines, ...).

See also

The expplot function for an "exponential distribution" plot (dedicated to the shape = 1 case), and the fweibull function for ML estimation of the parameters.

Examples

x <- rweibull(200, shape = 1.2, scale = 1)
weibplot(x, main = "Classical Weibull plot")

## Weibull lines
weibplot(x, shape = c(0.9, 1.3), scale = 1)

weibplot(x, shape = c(0.9, 1.3), scale = 1,
         labels = c("before", "after"))

weibplot(x, shape = c(0.9, 1.3), scale = 1,
         labels = c("before", "after"),
         mono = TRUE)