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, version 2.0.0

Abstract

This R package, seawaveQ, is designed for fitting a parametric regression model for assessing variability and trends in pesticide concentration in streams and was developed by Vecchia and others (2008), and subsequently refined and referred to as the“SEAWAVE-Q”model in several trend analyses (Ryberg and others, 2010; Sullivan and others, 2009; Vecchia and others, 2009). In these publications, “SEAWAVE-Q”stands for seasonal wave (SEAWAVE) with adjustment for streamflow (Q). The model was developed to“handle a number of difficulties often found in pesticide data, such as strong seasonality in response to use patterns, high numbers of concentrations below laboratory