The SSN2 package provides tools for spatial statistical modeling, parameter estimation, and prediction on stream (river) networks. SSN2 is the successor to the SSN package (Ver Hoef, Peterson, Clifford, & Shah, 2014), which was archived alongside broader changes in the -spatial ecosystem (Nowosad, 2023) that included 1) the retirement of rgdal (Bivand, Keitt, & Rowlingson, 2021), rgeos (Bivand & Rundel, 2020), and maptools (Bivand & Lewin-Koh, 2021) and 2) the lack of active development of sp (Bivand, Pebesma, & G��mez-Rubio, 2013). SSN2 maintains compatibility with the input data file structures used by the SSN package but leverages modern -spatial tools like sf (Pebesma, 2018). SSN2 also provides many useful features that were not available in the SSN package, including new modeling and helper functions, enhanced fitting algorithms, and simplified syntax consistent with other generic functions.
