R: Smoothing Spline with User-Specified Rigidity and Frequency...

ffcsaps {dplR} | R Documentation

## Smoothing Spline with User-Specified Rigidity and Frequency Cutoff

### Description

Applies a smoothing spline to `y` with rigidity determined by two parameters: frequency response `f` at a wavelength of `nyrs` years.

### Usage

    ffcsaps(y, x = seq_along(y), nyrs = length(y)/2, f = 0.5)

### Arguments

`y` | a `numeric` vector, typically a tree-ring series.
`x` | a `numeric` vector with the same length as `y`, typically giving the years of `y`.
`nyrs` | a number greater than 1, affecting the rigidity of the spline. When `f` is kept constant, a larger `nyrs` produces a more rigid spline. Defaults to `length(y)/2`.
`f` | a number between 0 and 1 giving the frequency response at a wavelength of `nyrs` years. When `nyrs` is kept constant, a smaller `f` produces a more rigid spline: At one extreme, `f = 0` causes the function to return the least-squares straight line fit to the data. At the other extreme, `f = 1` results in the natural spline, i.e. the function outputs `y`. The default value is 0.5.

### Details

This applies a smoothing spline similar to the spline applied in most dendrochronological software. See references for more information. See ‘Examples’ for a pointer to a PDF document including mathematical details about the function.

### Value

A filtered vector.

### Note

DendroLab website: https://dendrolaborg.wordpress.com/

### 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

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.

### See Also

`hanning`, `detrend`

### Examples

    library(graphics)
    library(utils)
    docFile <- system.file("doc", "math-dplR.pdf", package="dplR")
    cat("See the following PDF for mathematical details:\n")
    cat(docFile, sep="\n")
    ## Not run:
    if (interactive() && requireNamespace("Biobase")) {
        Biobase::openPDF(docFile)
    }
    ## Use series CAM011 from the Campito data set
    data(ca533)
    series <- ca533[, "CAM011"]
    series <- series[!is.na(series)]
    plot(series, type = "l", ylab = "Ring Width (mm)", col = "grey")
    lines(ffcsaps(series, nyrs = 32), col = "red", lwd = 2)
    lines(ffcsaps(series, nyrs = 64), col = "green", lwd = 2)
    lines(ffcsaps(series, nyrs = 128), col = "blue", lwd = 2)

    ## End(Not run)
    ## Use first series from the Mesa Verde data set
    data(co021)
    series <- co021[, 1]
    series <- series[!is.na(series)]
    plot(series, type = "l", ylab = "Ring Width (mm)", col = "grey")
    lines(ffcsaps(series, nyrs = 32), col = "red", lwd = 2)
    lines(ffcsaps(series, nyrs = 64), col = "green", lwd = 2)
    ## nyrs defaults to 0.5*length(series) == 347
    lines(ffcsaps(series), col = "blue", lwd = 2)
    legend("topright",
           c("Series", "nyrs=32", "nyrs=64",
             paste("Default nyrs (", length(series) / 2, ")", sep="")),
           fill=c("grey", "red", "green", "blue"))

[Package dplR version 1.7.2 Index]