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Open-File Report 2013–1255

National Water-Quality Assessment Program

seawaveQ—An R Package Providing a Model and Utilities for Analyzing Trends in Chemical Concentrations in Streams with a Seasonal Wave (seawave) and Adjustment for Streamflow (Q) and Other Ancillary Variables

By Karen R. Ryberg and Aldo V. Vecchia

Thumbnail of and link to report PDF (854 kB)Abstract

The seawaveQ R package fits a parametric regression model (seawaveQ) to pesticide concentration data from streamwater samples to assess variability and trends. The model incorporates the strong seasonality and high degree of censoring common in pesticide data and users can incorporate numerous ancillary variables, such as streamflow anomalies. The model is fitted to pesticide data using maximum likelihood methods for censored data and is robust in terms of pesticide, stream location, and degree of censoring of the concentration data. This R package standardizes this methodology for trend analysis, documents the code, and provides help and tutorial information, as well as providing additional utility functions for plotting pesticide and other chemical concentration data.

First posted December 30, 2013

For additional information, contact:
Director, North Dakota Water Science Center
U.S. Geological Survey
821 East Interstate Avenue
Bismarck, North Dakota 58503
http://nd.water.usgs.gov/

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Suggested citation:

Ryberg, K.R., and Vecchia, A.V., 2013, seawaveQ—An R package providing a model and utilities for analyzing trends in chemical concentrations in streams with a seasonal wave (seawave) and adjustment for streamflow (Q) and other ancillary variables: U.S. Geological Survey Open-File Report 2013–1255, 13 p., with 3 appendixes, http://dx.doi.org/10.3133/ofr20131255.

ISSN 2331-1258 (online)



Contents

Abstract

Introduction

Description of the seawaveQ Package

Statistical Methodology

Summary

Disclaimer

References Cited

Appendixes 1–3


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