The code base for IsoplotR’s graphical user interface (GUI) and its core data processing algorithms are surgically separated from each other. The command-line functionality is grouped in a lightweight package called IsoplotR, which has minimal dependencies and works on a basic R installation. It only uses commands that have been part of the R programming language for many decades and are unlikely to change in the future. In contrast, the GUI is written in html and Javascript and interacts with IsoplotR via an interface library. This interface is currently provided by the shiny package. shiny is free, open, and popular among R developers but has two important limitations: (1) it was created and is owned by a private company, which reduces the software’s future proofness; (2) shiny is a rather ‘bloated’ piece of code that does much more than is needed for IsoplotRgui. To avoid these issues, shinylight is a light-weight alternative to shiny that allows websites to call R functions in a similar fashion to the way in which node.js allows websites to use Javascript as a server language. Shinylight has been integrated in IsoplotRgui and all future software deliverables of the ‘Beyond Isoplot’ project, including the upcoming 'simplex' program for SIMS data processing.

This dataset contains raw data from synthetic and experimental velocity steps analyzed using the MATLAB routine ‘steadystate.m’, as presented by Giacomel, P., Faulkner, D.R., Lambert, V., Allen, M.J (2024): ‘steadystate: A MATLAB-based routine for determining steady-state friction conditions in the framework of rate- and state- friction analysis’ – GSA, Geosphere. The data is provided in .zip folder containing the Velocity Steps and the outputs from steadystate.m, along with the scripts used to generate the figures shown in the Manuscript and Supplementary Material. The folder ‘Velocity_Steps’ notably contains the complete suite of mechanical data (subfolder ‘Mechanical_Data), the modelled rate- and state- friction parameters (subfolder ‘Modelled_RSF_Parameters SlipLaw’) obtained by assuming steady state at different displacements, as well as the linear detrended end members (i.e., at short to large displacements) fitted via inverse modelling (subfolder ‘Detrended_Velocity_Steps + Fit-Inversions’). Such observations were foundational for the development of the steadystate.m routine. Each subfolder is accompanied by a README.txt file that reports on the link between the raw .txt data with the MATLAB scripts generating the associated figures. For the sepiolite fault gouge used during the friction velocity steps, please refer to: Sánchez-Roa, C., Jiménez-Millán, J., Abad, I., Faulkner, D. R., Nieto, F., and García-Tortosa, F. J., 2016, Fibrous clay mineral authigenesis induced by fluid-rock interaction in the Galera fault zone (Betic Cordillera, SE Spain) and its influence on fault gouge frictional properties: Applied Clay Science, v. 134, p. 275-288.