Calculate Gleichläufigkeit

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Description

This function calculates the matrix of Gleichläufigkeit for a given set of tree-ring records.

Usage

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glk(x)

Arguments

x

a data.frame of tree-ring data with records in columns, and years as rows.

Details

Gleichläufigkeit is a classical agreement test based on sign tests (Eckstein and Bauch, 1969). This function implements Gleichläufigkeit as the pairwise comparison of all records in data set, and thus returns a matrix whose upper triangle reports the Gleichläufigkeit of each possible combination of records. The global Gleichläufigkeit can be calculated as mean(glk(x), na.rm = TRUE). This implementation improves the original formulation inasmuch as the case of neighbouring identical measurements in the same years is accounted for. Here, it is treated as full agreement, in contrast to only partial agreement in the original formulation.

Value

A matrix with the Gleichläufigkeit for all possible combinations of records. If two curves have less than 3 years of overlap, Gleichläufigkeit cannot be computed, and NA is returned.

Author(s)

Christian Zang. Patched and improved by Mikko Korpela. Improved by Allan Buras.

References

Eckstein, D. and Bauch, J. (1969) Beitrag zur Rationalisierung eines dendrochronologischen Verfahrens und zur Analyse seiner Aussagesicherheit. Forstwissenschaftliches Centralblatt, 88(1), 230–250.

Schweingruber, F. H. (1988) Tree rings: basics and applications of dendrochronology. Kluwer Academic Publishers, Dordrecht, Netherlands, 276 p.

Examples

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library(utils)
data(ca533)
ca533.glk <- glk(ca533)
mean(ca533.glk, na.rm = TRUE)

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