lmom: evplot – R documentation

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evplot

Extreme-value plot

Description

evplot draws an “extreme-value plot”, i.e. a quantile-quantile plot in which the horizontal axis is the quantile of an extreme-value type I (Gumbel) distribution.

evdistp adds the cumulative distribution function of a distribution to an extreme-value plot.

evdistq adds the quantile function of a distribution to an extreme-value plot.

evpoints adds a set of data points to an extreme-value plot.

Usage

evplot(y, ...)

## Default S3 method:
evplot(y, qfunc, para, npoints = 101, plim, xlim = c(-2, 5),
       ylim, type,
       xlab = expression("Reduced variate,  " * -log(-log(italic(F)))),
       ylab = "Quantile", rp.axis = TRUE, ...)

evdistp(pfunc, para, npoints = 101, ...)
evdistq(qfunc, para, npoints = 101, ...)

evpoints(y, ...)

Arguments

`y`	Numeric vector. The data values in the vector are plotted on the extreme-value plot.
`qfunc`	A quantile function. The function is drawn as a curve on the extreme-value plot.
`pfunc`	A cumulative distribution function. The function is drawn as a curve on the extreme-value plot.
`para`	Distribution parameters for the quantile function `qfunc` or cumulative distribution function `pfunc`. If `pfunc` or `qfunc` is the standard R form of quantile function, `para` should be a list. If `pfunc` or `qfunc` is the `qua...` form of quantile function used throughout the lmom package, `para` should be a numeric vector. In `evplot`, `para` is not used if `qfunc` is omitted.
`npoints`	Number of points to use in drawing the quantile function. The points are equally spaced along the x axis. Not used if `qfunc` is omitted.
`plim`	X axis limits, specified as probabilities.
`xlim`	X axis limits, specified as values of the Gumbel reduced variate -log(-log(F)), where F is the nonexceedance probability. Not used if `plim` is specified.
`ylim`	Y axis limits.
`type`	Plot type. Determines how the data values in `y` are plotted. Interpreted in the same way as argument `type` of function `plot`, i.e. `"p"` for points, `"b"` for points connected by lines, etc.
`xlab`	X axis label.
`ylab`	Y axis label.
`rp.axis`	Logical. Whether to draw the “Return period” axis, a secondary horizontal axis.
`...`	Additional arguments are passed to the plotting routine.

Arguments of cumulative distribution functions and quantile functions

pfunc and qfunc can be either the standard R form of cumulative distribution function or quantile function (i.e. for a distribution with r parameters, the first argument is the variate x or the probability p and the next r arguments are the parameters of the distribution) or the cdf... or qua... forms used throughout the lmom package (i.e. the first argument is the variate x or probability p and the second argument is a vector containing the parameter values).

Note

Data points are plotted at the Gringorten plotting position, i.e. the i'th smallest of n data points is plotted at the horizontal position corresponding to nonexceedance probability (i-0.44)/(n+0.12).

Author(s)

J. R. M. Hosking jrmhosking@gmail.com

Examples

# Extreme-value plot of Ozone from the airquality data
data(airquality)
evplot(airquality$Ozone)

# Fit a GEV distribution and add it to the plot
evdistq(quagev, pelgev(samlmu(airquality$Ozone)))

# Not too good -- try a kappa distribution instead
evdistq(quakap, pelkap(samlmu(airquality$Ozone)), col="red")

lmom

L-Moments

v2.8

Common Public License Version 1.0

Authors

J. R. M. Hosking

Initial release

2019-03-11