Supplement 1. The Corrigan and the Nile Creek data sets and the S-PLUS functions for fitting the piecewise-regression models used in the paper.

File ListAll files at once

pw_regression.zip

Data files

corrigan_data.txt
- tab-delimited ASCII file of presence/absence
data at the Corrigan site.

nile_creek_data.txt
- tab-delimited ASCII file of presence/absence
data at the Nile Creek site.

S-PLUS files

pwreg_fns.txt
- ASCII file of S-PLUS functions
for fitting the piecewise regression models

fn_calls.txt
- ASCII file of example function calls (will recreate most of the results
in the paper)

DescriptionThe files corrigan_data.txt
and nile_creek_data.txt are tab-delimited
ASCII files of the data used. Tree species are split into height categories (height
>1.3 m, or <1.3 m). In both files, columns 2–13 are from transect
#1, columns 14–25 are from transect #2, and columns 26–37 are from transect
#3. S-PLUS functions for fitting all piecewise-regression models in the paper
(sharp, hyperbolic-tangent, bent-hyperbola, and bent-cable piecewise-regression
models) are available in pwreg_fns.txt.
The file also contains additional functions for deriving and plotting confidence
intervals for an estimate of the breakpoint. Import these functions into a S-PLUS
session using the internal S-PLUS function source. The functions are known to
work in S-PLUS version 4.5 and 6.1 for Windows. The results for the case study
can then be recreated using the commands listed in fn_calls.txt.
As written, the function calls assume that the first PCA axis for the Corrigan
data has been extracted and called corpapca.df,
that the first PCA axis for the Nile Creek data has been extracted and called
nilpapca.df, and that a vector
of distances from edge has been created and called distance.