R: Regional Curve Standardization

rcs {dplR} | R Documentation

## Regional Curve Standardization

### Description

Detrend multiple ring-width series simultaneously using a regional curve.

### Usage

    rcs(rwl, po, nyrs = NULL, f = 0.5, biweight = TRUE, ratios = TRUE,
        rc.out = FALSE, make.plot = TRUE, ..., rc.in = NULL, check = TRUE)

### Arguments

`rwl` | a `data.frame` with series as columns and years as rows such as that produced by `read.rwl`
`po` | a `data.frame` containing two variables. Variable one (`series` in the example below) gives the series ID as either `character`s or `factor`s. These must exactly match `colnames(rwl)`. Variable two (`pith.offset` in the example below) must be integral values and give the years from the beginning of the core to the pith (or center) of the tree. The minimum value is 1.
`nyrs` | a number giving the rigidity of the smoothing spline, defaults to 0.1 of length of the maximum cambial age (i.e., the length of the regional curve) if `nyrs` is `NULL`.
`f` | a number between 0 and 1 giving the frequency response or wavelength cutoff. Defaults to 0.5.
`biweight` | `logical` flag. If `TRUE` then a robust mean is calculated using `tbrm`.
`ratios` | `logical` flag. If `TRUE` (the default) then indices are calculated by division, if `FALSE` indices are calculated by subtraction.
`rc.out` | `logical` flag. Returns the regional curve along with the ring-width indices if `TRUE`.
`make.plot` | `logical` flag. Makes plots of the raw data and regional curve if `TRUE`.
`...` | other arguments passed to `plot`.
`rc.in` | for internal use.
`check` | a `logical` flag. Bypass input checks by setting this to `FALSE`.

### Details

This method detrends and standardizes tree-ring series by calculating an age-related growth curve specific to the `rwl`. The detrending is the estimation and removal of the tree’s natural biological growth trend. The standardization is done by either dividing each series by the growth trend or subtracting the growth trend from each series to produce units in the dimensionless ring-width index (RWI). The option to produce indices by subtraction is intended to be used on series that have been subject to variance stabilization (e.g., using `powt`).

The spline approach uses an n-year spline where the frequency response is 0.50 at a wavelength of 10 percent of the maximum cambial age unless specified differently using `nyrs` and `f` in the function `ffcsaps`.

This attempts to remove the low frequency variability that is due to biological or stand effects. See the references below for further details on detrending in general, and Biondi and Qeadan (2008) for an explanation of RCS.

### Value

A `data.frame` containing the dimensionless and detrended ring-width indices with column names, row names and dimensions of `rwl`. If `rc.out` is `TRUE` then a `list` will be returned with a `data.frame` containing the detrended ring widths as above and a `vector` containing the regional curve.

### Note

DendroLab website: http://dendrolab.org/

### Author(s)

Code provided by DendroLab based on programming by F. Qeadan and F. Biondi, University of Nevada Reno, USA and adapted for dplR by Andy Bunn. Patched and improved by Mikko Korpela.

### References

Biondi, F. and Qeadan, F. (2008) A theory-driven approach to tree-ring standardization: Defining the biological trend from expected basal area increment. Tree-Ring Research, 64(2), 81–96.

Cook, E. R. and Kairiukstis, L. A., editors (1990) Methods of Dendrochronology: Applications in the Environmental Sciences. Springer. ISBN-13: 978-0-7923-0586-6.

Fritts, H. C. (2001) Tree Rings and Climate. Blackburn. ISBN-13: 978-1-930665-39-2.

### See Also

`detrend`, `chron`, `cms`, `ffcsaps`

### Examples

    library(utils)
    data(gp.rwl)
    data(gp.po)
    gp.rwi <- rcs(rwl = gp.rwl, po = gp.po, biweight = TRUE,
                  rc.out = TRUE, make.plot = FALSE)
    str(gp.rwi)
    gp.rwi <- rcs(rwl = gp.rwl, po = gp.po, biweight = TRUE,
                  make.plot = TRUE, main = "Regional Curve")

[Package dplR version 1.7.1 Index]