dplR (version 1.4.9)

rwi.stats: Calculates Summary Statistics on Detrended Ring Width Series

Description

This function calculates descriptive statistics on a data.frame of (usually) ring-width indices.

Usage

rwi.stats(rwi, ids = NULL, period = c("max", "common"))

Arguments

rwi

a data.frame with detreneded and standardised ring width indices as columns and years as rows such as that produced by detrend.

ids

a optional data.frame with column one named tree giving a numeric id for each tree and column two named core giving a numeric id for each core. Defaults to one core per tree as data.frame(tree=

period

a character string, either common or max indicating whether correlations should be limited to complete observations over the period common to all cores or the maximum pairwise overlap. See Details of

Value

• A data.frame containing the following: n.tot total number of unique combinations of the input series (i.e., n*n-1/2), n.wt total number of unique combinations of the within-tree series, n.bt total number of unique combinations of the between-tree series, rbar.tot the mean of all correlation between different cores, rbar.wt the mean of the correlations between series from the same tree over all trees, rbar.bt the mean interseries correlation between all series from different trees, c.eff the effective number of cores, rbar.eff the effective signal calculated as rbar.bt / (rbar.wt + (1-rbar.wt) / c.eff), eps the expressed population signal.

Details

This calculates a variety of descriptive statistics commonly used in dendrochronology. For correctly calculating the statistics on within and between series variability, an appropriate mask must be provided that identifies each series with a tree as it is common for dendrochronologists to take more than one core per tree. The function read.ids is be helpful for creating a mask based on the series id. Note that period=common can produce NaN for many of the stats if there is no common overlap period among the cores. This happens especially in chronologies with floating subfossil samples (e.g., ca533). Some of the statistics are specific to dendrochronology (e.g., the effective number of cores or the expressed population signal). Users unfamiliar with these should see Cook and Kairiukstis (1990) and Fritts (2001) for further details.

References

Cook, E.R. and Kairiukstis, L.A. (1990) Methods of Dendrochronology: Applications in the Environmental Sciences. Springer. ISBN-13: 978-0792305866. Fritts, H.C. (2001) Tree Rings and Climate. Blackburn. ISBN-13: 978-1930665392.

See Also

detrend, cor, read.ids, rwi.stats.running

Examples

data(ca533)
  ca533.rwi <- detrend(rwl = ca533, method = "ModNegExp")
  ca533.ids <- read.ids(ca533, stc=c(3,2,3))
  rwi.stats(ca533.rwi, ca533.ids)