SISUS is a Bayesian statistical model and software aiming to provide a comprehensive solution to stable isotope sourcing inference and prediction problems.
You can use SISUS today by downloading the workbook template on the left, inputting your data, then submitting in the Execute page to return plots and numerical summaries.
Awards: First place, Graduate Poster division, UNM Biology 16th Annual Research Day
Citing SISUS website documents:
e-mail: "Erik Barry Erhardt" <erik AT StatAcumen.com>
To estimate feasible proportional contributions of sources to a mixture using stable isotope data.
Mass-balance mixing models for stable isotope sourcing provide a mechanistic, and hence predictive, foundation for describing animal ecology and other applications where sources assimilate into a mixture. The goal of the mixing models described here is to estimate feasible proportions of biomass consumed of sources by a consumer. The mixing models used in stable isotope sourcing problems have a common linear structure, which we emphasize here. These models define the relationship between the isotopic data space and the source-proportion solution space. Often, the number of sources n is many more than the number of stable isotopes k, n > k + 1, resulting in an infinite number of source-proportion solutions, a region we call the solution polytope. The most popular software for providing solutions to underconstrained mixing models is IsoSource (Phillips and Gregg, 2003), a deterministic algorithm for providing approximate solutions to represent the solution polytope. Here, we describe an algorithm implemented as SISUS software for providing a user-specified number of probabilistic exact solutions quickly which accurately represents the solution polytope. Both methods provide qualitatively similar results, though the differences arguably favor the probabilistic approach. Additionally, we show how IsoSource can be used to provide approximate solutions to the Assimilation Efficiency Concentration-Dependent Mixing Model, a more developed model than the Basic Mixing Model. SISUS software is freely available at http://StatAcumen.com/sisus.
Microsoft Excel or other software (such as OpenOffice.org for Mac OS X, Linux, etc.) to read, modify, and write the input workbook in xls format.
When using OpenOffice.org, if an error occurs, first try setting the cell format of all numeric fields to Numeric.
