regsamlmu {lmomRFA}

Sample L-moments of multiple data sets

Description

Computes the “unbiased” sample L-moments and L-moment ratios of multiple sets of data stored in a list or matrix. Following the paradigm of regional frequency analysis, we regard the data sets as coming from different measurement sites.

Usage

regsamlmu(x, nmom = 5, sort.data = TRUE, lcv = TRUE)

Arguments

x

A list of numeric vectors, or a numeric matrix.

nmom

Number of L-moments to be computed.

sort.data

Logical: whether each data set should be sorted.

lcv

Logical. If TRUE, the second L-moment will be expressed as a fraction of the mean, i.e. the computed value will be the sample L-CV t=\ell_2/\ell_1. If FALSE, the second L-moment will simply be the sample L-scale value \ell_2.

Details

Sample L-moments are computed for each data set. The calculations use samlmu internally. If x is a list, each list element should contain data for one site and the names of the list elements should be the site names. If x is a matrix, each column should contain data for one site and the column names should be the site names.

Value

An object of class regdata. It is a data frame with columns "name" and "n", containing respectively the site names and the number of non-missing data values at each site, and further columns containing the L-moments and L-moment ratios, in the order \ell_1, t (or \ell_2), t_3, t_4, etc.

Note

The default parameter values are chosen to be convenient for the regional frequency analysis methods described by Hosking and Wallis (1997). Note that the number of L-moments and the choice of whether to return L-CV or L-scale are different from the defaults for samlmu.

Users of the LMOMENTS Fortran package, version 3.04, should note that its PROGRAM XFIT by default uses plotting-position estimators of L-moment ratios, which give different results from the “unbiased” estimators used by regsamlmu (and by all other functions in package lmomRFA).

Author(s)

J. R. M. Hosking [e-mail]

References

Hosking, J. R. M., and Wallis, J. R. (1997). Regional frequency analysis: an approach based on L-moments. Cambridge University Press.

Examples

data(Maxwind)       # a list
regsamlmu(Maxwind)

data(airquality)    # a data frame
regsamlmu(airquality[1:4])