R: Chronology Stripping by EPS

strip.rwl {dplR} | R Documentation

## Chronology Stripping by EPS

### Description

EPS-based chronology stripping after Fowler & Boswijk 2003.

### Usage

    strip.rwl(rwl, ids = NULL, verbose = FALSE, comp.plot = FALSE,
              legacy.eps = FALSE)

### Arguments

`rwl` | a `data.frame` of raw tree-ring widths series, such as that produced by `read.rwl` or `read.fh`
`ids` | an 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. This is passed on to `rwi.stats`. See its manual for the meaning of the default value `NULL` and more information.
`verbose` | `logical` flag, indicating if the EPS calculated at each step and other details should be printed on the console during the chronology stripping process
`comp.plot` | `logical` flag, indicating if a diagnostic plot with year-wise stripped and unstripped EPS should be drawn (see details below)
`legacy.eps` | `logical` flag, indicating if the EPS will be calculated with `rwi.stats` (`FALSE`, the default) or `rwi.stats.legacy` (`TRUE`)

### Details

The EPS-based chronology stripping is implemented after Fowler & Boswijk 2003: First, all series are standardized using a double detrending procedure with splines and frequency cutoffs of 50% at 20 and 200 years. Then, EPS is calculated for the chronology including all (remaining) series. In each iteration, the algorithm calculates leave-one-out EPS values, and the series whose removal increases overall EPS the most is discarded. This is repeated until no further increase in EPS is gained by discarding a single series. The procedure is then repeated in the opposite direction, i.e., the reinsertion of each previously removed series into the `data.frame` is considered. In each iteration, the series (if any) whose reinsertion increases EPS the most is reinserted. As a last step, EPS is calculated for each year of the stripped and original chronology including all series. If `comp.plot` is set to `TRUE`, a diagnostic plot is shown for the year-wise comparison.

When verbose output is chosen, the EPS values for all leave-one-out (or back-in) chronologies are reported. If discarding or re-inserting a single series leads to an improvement in EPS, this series is marked with an asterisk.

### Value

The functions returns a `data.frame` of raw tree-ring widths, where series that do not contribute to an overall improvement in EPS are left out.

### Author(s)

Christian Zang. Patched and improved by Mikko Korpela.

### References

Fowler, A. and Boswijk, G. (2003) Chronology stripping as a tool for enhancing the statistical quality of tree-ring chronologies. Tree-Ring Research, 59(2), 53–62.

### See Also

`rwi.stats`

### Examples

    library(utils)
    data(anos1)
    anos1.ids <- read.ids(anos1, stc = c(4, 3, 1))
    srwl <- strip.rwl(anos1, ids = anos1.ids, verbose = TRUE)
    tail(srwl)

[Package dplR version 1.7.2 Index]