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NADA for R: Nondetects and Data Analysis for the R statistical computing environment

Description:

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.

Contents:

• Statistical Methods
  • Robust Regression on Order Statistics (Robust ROS)
  • Empirical cumulative distribution functions (ECDFs) using Kaplan-Meier methods
  • Nonparametric hypothesis testing based on ECDFs and rank-sum methods.
  • Maximum Likelihood Estimation summary statistic, and regression methods.
  • Censored probability plots
  • Censored boxplots
• Miscellaneous
  • Generic summary, printing, and plotting functions.
  • All statistical methods have common query and prediction functions that allow the computation of summary statistics and prediction of modeled values.

References:

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.

Installing NADA for R:

The primary requirement for running the software is a working installation of the R environment. R can be obtained at http://www.r-project.org/.


Once R is installed and the machine has a functioning internet connection, the NADA package may be automatically installed using the following command:


> install.packages("NADA")


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).