Compute Adjusted Latewood

Description

Separate earlywood and latewood chronologies can be developed from the annual growth rings, which can then be used to develop separate cool- and warm-season reconstructions, respectively (e.g., Stahle et al. 2009). Unfortunately, there is strong autocorrelation between the earlywood and the latewood. Moreover, the seasonal response of the earlywood may slightly overlap with latewood. Thus, it is necessary to remove the dependency of latewood on earlywood, and this can be accomplished by taking the residuals from a linear regression model of latewood regressed on earlywood (Meko and Baisan 2001). This tool computes the adjusted latewood chronology by either simple linear regression or robust regression (see "Parameters" below). The output consists of the Pearson correlation computed between the earlywood and the latewood in addition to the new adjusted latewood chronology.

Input

File
Select the input data to analyze by clicking on "Browse" and navigating to the proper file.

Input Data Format
Year / Data

Each "/" is a tab (i.e., data should be tab-delimited). Missing Data should be denoted as "-99".

Start Row
This input is the row number where the main data to be processed begin in the input file selected above. An example of how row numbers are entered is shown in Figure 2 located in the Running Dendro Tools topic.

Parameters

Ordinary Least Squares Regression / Assume Normal Distribution
Select this option to have Dendro Tools derive the adjusted latewood using simple linear regression. After the residuals are computed, a normal distribution is assummed and the results are normalized. The mean and standard deviation from the original latewood chronology are then restored to the new adjusted latewood chronology. Finally, a constant of 1.0 is added to remove any remaining negative values.

Robust Regression / Distribution Independent
Select this option to have Dendro Tools derive the adjusted latewood using robust regression. There are various ways to perform robust regression, but Dendro Tools uses the defaults available in R (see rlm documentation in MASS library; R Core Development Team 2013). After the residuals are computed, the results are "normalized" using the median and interquartile range (i.e., this parameter does not assume a normal distribution). The median and interquartile range from the original latewood chronology are then restored to the new adjusted latewood chronology. Finally, a constant of 1.0 is added to remove any remaining negative values.

Output

File
Select or enter the name of the file where the results will be stored.

Header
Information entered here will be output in the first line of the output file.