regken: Trend Test

In USGS-R/smwrStats: R functions to support statistical methods in water resources

Trend Test

Description

Computes the regional Kendall trend test with Sen slope estimator.

Usage

regken(series, correct = nrow(series) > 9)

Arguments

series	a numeric matrix with rows representing the annual observations and columns representing the sites. Missing values are permitted.
correct	logical, if TRUE, then apply the correction for cross correlation among sites. if FALSE, then do not apply the correction.

Value

An object of class "htest" also inhereting class "seaken" containing the following components:

method	a description of the method.
statistic	the value of Kendall's tau.
p.value	the p-value. See Note.
p.value.raw	the p-value computed without correction for cross correlation. See Note.
p.value.corrected	the p-value computed with correction for cross correlation. See Note.
estimate	a named vector containing the Sen estimate of the slope in units per year, the median value of the data, and the median value of time.
data.name	a string containing the actual name of the input series with the number of years and sites
alternative	a character string describing alternative to the test ("two.sided").
null.value	the value for the hypothesized slope (0).
nyears	the number of years.
nseasons	the number of sites
series	the data that was analyzed.
seasonnames	the names of the sites

Note

The value of p.value is p.value.raw if there are fewer than 10 years of data and is p.value.corrected otherwise.

The regional Kendall is described in Douglas and others (2000) and Helsel and others (2006). The adjustment for spatial correlation used in regken is based on equation 13 in Douglas and others (2000) and uses the Spearman correlation to account for monotonic correlations.

References

Douglas, E.M., Vogel, R.M., and Kroll, C.N., 2000, Trends in floods and low flows in the United States: impact of spatial correlation: Journal of Hydrology, v. 240, p. 90–105.

Helsel, D.R., Mueller, D.K., and Slack, J.R., 2006, Computer program for the Kendall family of trend tests: U.S. Geological Survey Scientific Investigations Report 2005–5275, 4 p.

See Also

seaken

Examples

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USGS-R/smwrStats documentation built on Oct. 11, 2022, 6:15 a.m.