NEWS

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IsingSampler 0.4.0

• Added BlumeCapelSampler(), a wrapper around IsingSampler() for the Blume-Capel model: an Ising model with an additional on-site quadratic ("single-ion anisotropy" / crystal-field) term entering the Hamiltonian as delta_i * s_i^2. By default it uses the spin-1 response options c(-1, 0, 1) and requires the quadratic parameter 'delta'.
• IsingSampler(), IsingLikelihood(), IsingSumLikelihood() and IsingStateProb() gained a 'delta' argument (default 0, i.e. the ordinary Ising model). 'delta' may be a single value (recycled over nodes) or one value per node, exactly like 'thresholds'; a single 'thresholds' value is now likewise recycled over nodes. A positive delta favours response options near zero, a negative delta favours the extreme options.
• The 'delta' term only has an identifiable effect with more than two response options. With two response options it is folded into the thresholds (and is constant, hence has no effect, for symmetric responses such as c(-1, 1)); method = "CFTP" therefore remains binary-only and accounts for delta exactly via this folding.

IsingSampler 0.3.1

• Response options may now be any numeric values, including non-integers (e.g. seq(-1, 1, by = 0.5)). The sampler (methods "MH", "CFTP" and "direct") and the distribution functions all work with real-valued responses; in that case states are returned as a numeric (double) matrix. Integer-valued responses continue to return integer matrices, so existing binary/ordinal use is unchanged. Internally states, response options, the 'constrain' matrix and the sampled output are now double-valued throughout the C++ code.
• IsingSampler, IsingLikelihood, IsingSumLikelihood, IsingStateProb and IsingEntrophy support more than two response options (e.g. c(-1L, 0L, 1L) or 1:5). Sampling with method = "MH" uses the categorical (softmax) generalization of the binary conditional and initializes the chain uniformly over all response options; method = "direct" and the likelihood functions sum over all response combinations. The pairwise interaction enters the Hamiltonian as J_ij * s_i * s_j and each node keeps a single threshold. Binary (two-level) behaviour is unchanged.
• method = "CFTP" remains restricted to two response options (with an informative error for more than two), but now also works with two non-integer responses.
• The 'responses' argument is now validated: a clear error is given when it contains fewer than two options or any non-numeric or missing (NA) values.
• IsingEntrophy and NodeInformation now use the current dplyr API (group_by()/summarise()), fixing an error under recent dplyr versions.
• Removed the obsolete src/Makevars and src/Makevars.win (the deprecated Rcpp:::LdFlags() call is no longer needed); the package now passes R CMD check --as-cran without warnings.

IsingSampler 0.2.4 (2025-05-13)

• Fixed URL in DESCRIPTION

IsingSampler 0.2.2

• Small change to help file
• Added thresholding and minimum sum score correction to EstimateIsing Uni method
• 'uni' is now the default for EstimateIsing

IsingSampler 0.2.1 (2020-01-25)

• Added an option to IsingLikelihood to return the potential of each state

IsingSampler 0.2 (2015-03-02)

• Added methods for estimating the Ising model without regularization, see ?EstimateIsing