The baytrends package was developed to enable users to evaluate long-term trends in the Chesapeake Bay using a Generalized Additive Modeling (GAM) approach. The model development includes selecting a GAM structure to describe nonlinear seasonally-varying changes over time, incorporation of hydrologic variability via either a river flow or salinity, the use of an intervention to deal with method or laboratory changes suspected to impact data values, and representation of left- and interval-censored data. This approach, which is fully transferable to other systems, allows for Chesapeake Bay water quality data to be evaluated in a statistically rigorous, yet flexible way to provide insights to a range of management- and research-focused questions. Methodology described in Murphy, RR, E Perry, J Harcum, and J Keisman 2019 A Generalized Additive Model approach to evaluating water quality: Chesapeake Bay case study. Environmental Modelling & Software, 118 (2019) 1-13. <>.


This software program is preliminary or provisional and is subject to revision. This software program is for testing only, no warranty, expressed or implied, is made as to the accuracy and functioning of the program and related program material nor shall the fact of distribution constitute any such warranty, and no responsibility is assumed in connection therewith. This software is provided 'AS IS.