Annual maximum streamflow in central Appalachia
The data on annual maximum streamflow at 104 gaging stations in the central Appalachia region of the United States contains the sample L-moments ratios (L-CV, L-skewness and L-kurtosis) as used by Hosking and Wallis (1997) to illustrate regional freqency analysis (RFA).
A data frame with 104 observations on the following 3 variables:
L-coefficient of variation
L-coefficient of skewness
L-coefficient of kurtosis
The sample L-moment ratios (L-CV, L-skewness and L-kurtosis) of a site are regarded as a point in three dimensional space.
Hosking, J. R. M. and J. R. Wallis (1997), Regional Frequency Analysis: An Approach Based on L-moments. Cambridge University Press, p.175–185
Neykov, N.M., Neytchev, P.N., Van Gelder, P.H.A.J.M. and Todorov V. (2007), Robust detection of discordant sites in regional frequency analysis, Water Resources Research, 43, W06417, doi:10.1029/2006WR005322, http://www.agu.org/pubs/crossref/2007/2006WR005322.shtml
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data(Appalachia) # plot a matrix of scatterplots pairs(Appalachia, main="Appalachia data set", pch=21, bg=c("red", "green3", "blue")) mcd<-CovMcd(Appalachia) mcd plot(mcd, which="dist", class=TRUE) plot(mcd, which="dd", class=TRUE) ## identify the discordant sites using robust distances and compare ## to the classical ones mcd <- CovMcd(Appalachia) rd <- sqrt(getDistance(mcd)) ccov <- CovClassic(Appalachia) cd <- sqrt(getDistance(ccov)) r.out <- which(rd > sqrt(qchisq(0.975,3))) c.out <- which(cd > sqrt(qchisq(0.975,3))) cat("Robust: ", length(r.out), " outliers: ", r.out,"\n") cat("Classical: ", length(c.out), " outliers: ", c.out,"\n")
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