detect_sni: Calculate signal-to-noise index (SNI) for a charcoal record

In HOPE-UIB-BIO/R-Ratepol-package: R-Ratepol: Estimating Rate of Change in Temporal Sequences

Calculate signal-to-noise index (SNI) for a charcoal record

Description

Code obtained and from Kelly et al. 2010

Usage

detect_sni(CharData, BandWidth)

Arguments

CharData	Matrix of input data with one row per sample, containing: Column 1: age associated with the sample (yr) Column 2: charcoal accumulation rate (CHAR) of the sample (pieces/cm^2/yr) Column 3: threshold value (pieces/cm^2/yr)
BandWidth	= Width of moving window for computing SNI

Details

This function computes SNI as described in Kelly et al. 2010. Note that your data must be interpolated to constant sample resolution (yr/sample) before input to the function. The function makes no assumption about prior analysis on the input CHAR series, i.e. any background and threshold methods may be used. However, input data should still be consistent with the interpretation that a CHAR value (column 2) greater than the corresponding threshold value (column 3) is a "signal" sample, whereas a CHAR value below the threshold is "noise". Refer to Kelly et al. 2010 for details and discussion.

Value

SNI_output is a data list containing the computed SNI and related data, with one row for each row in the input variable CharData:

• SNI = the SNI computed for each sample

• winInd = indexes of the first and last samples included in each moving window. E.g. SNI_output["winInd", X] == (A, B) indicates that the moving window used to calculate SNI for the Xth sample contained all samples between A and B, inclusive.

• popN = the CHAR values of all samples in the noise (N) population (samples in the moving window with CHAR below threshold)

• popS = the CHAR values of all samples in the signal (S) population (samples in the moving window with CHAR at or above threshold)

• meanN = mean CHAR of the samples in popN

• stdN = standard deviation of the samples in popN

• CF = the "correction factor" used in computing SNI. Equal to (v - 2)/v ,where v is the number of samples in popN

References

Kelly RF, Higuera PE, Barrett CM, Feng Sheng H. 2011 A signal-to-noise index to quantify the potential for peak detection in sediment-charcoal records. Quat. Res. 75, 11-17. (doi:10.1016/j.yqres.2010.07.011)

HOPE-UIB-BIO/R-Ratepol-package documentation built on March 6, 2024, 7:10 a.m.