Water Resources of the United States
NADA for R is a library package for the R environment for graphics and statistics. The package contains data and analysis methods described in the book Nondetects and Data Analysis: Statistics for Censored Environmental Data , Helsel (2005) -- See references below.
NADA for R can be used to plot data, generate summary statistics, compute exceedance probabilities, and perform hypothesis tests, on data containing multiple censoring thresholds (a.k.a nondetects, or less-thans).
All functions within NADA for R are presented within a clear, consistent, and easy to use framework.
Dennis R. Helsel, 2005. Nondetects and Data Analysis: Statistics for Censored Environmental Data. John Wiley and Sons, New York, 250p.
Lopaka Lee and Dennis Helsel, 2005. Statistical analysis of water-quality data containing multiple detection limits I: S-language software for regression on order statistics. Computers and Geoscience, 31, 1241-1248.
Lopaka Lee and Dennis Helsel, 2005. Baseline Models of Trace Elements in Major Aquifers of the United States. Applied Geochemistry, 20, 1560-1570.
Lopaka Lee and Dennis Helsel, (in press) Statistical analysis of water-quality data containing multiple detection limits II: S-language software for nonparametric distribution modeling and hypothesis testing. Computers and Geoscience.
The primary requirement for running the software is a working
installation of the R environment. R can be obtained at
Once R is installed and the machine has a functioning internet connection, the NADA package may be automatically installed using the following command:
Both R and NADA for R are Free Software and can be obtained, used, modified and distributed under the terms of the GNU General Public License (version 2 or newer).