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Comparison · Infra & APIs
BAS vs modsem
A side-by-side editorial comparison of BAS and modsem — release velocity, themes, recent moves, and the top alternatives to consider.
BAS vs modsem: at a glance
What is BAS?
A Bayesian model-averaging package spending its 2.0 on memory, not methods.
BAS performs Bayesian variable selection and model averaging for linear and generalized linear models, sampling from a model space too large to enumerate. The visible history splits cleanly: 2023-2024 added sampling machinery — an adaptive independent MCMC sampler with Horvitz-Thompson estimation, hereditary-constraint counting — while 2.0.0 in late 2025 reworked how sampler output is allocated in C. The 2.0.2 patch is a PROTECT fix for rchk warnings.
What is modsem?
modsem is grinding latent interaction models toward Mplus parity, one estimator at a time.
modsem fits interaction and quadratic effects between latent variables in R, offering both product-indicator approaches (modsem_pi) and distribution-analytic ones (modsem_da, covering LMS and QML). Releases land roughly monthly and are dense pull-request lists. The recent line is dominated by the LMS approach: gradient refactors, parallel E-steps, composite construct support, and careful handling of residual covariances between latent variables.
BAS vs modsem: editorial side-by-side
BAS
0.0INFRA · APIS
A Bayesian model-averaging package spending its 2.0 on memory, not methods.
◆ Current state
BAS performs Bayesian variable selection and model averaging for linear and generalized linear models, sampling from a model space too large to enumerate. The visible history splits cleanly: 2023-2024 added sampling machinery — an adaptive independent MCMC sampler with Horvitz-Thompson estimation, hereditary-constraint counting — while 2.0.0 in late 2025 reworked how sampler output is allocated in C. The 2.0.2 patch is a PROTECT fix for rchk warnings.
◆ Where it's heading
Memory is the binding constraint and the releases say so directly. The hereditary-constraint counter, the GROW option, and the replacement of over-allocation with resizing all attack the same problem: n.models is a guess, and guessing high wastes memory on problems where few unique models are actually visited. The 2.0.0 work was additionally forced by R tightening its C API against non-API calls like SETLENGTH, a constraint every C-heavy CRAN package has been absorbing. Method development has been quiet since 1.7.x.
◆ Prediction
The 1.7.5 notes call the hereditary-constraint counting a first step and say future updates will cover other constraint types, including polynomials, which remain unhandled. That is the one concrete commitment in this history, though nothing since has returned to it.
modsem
0.0INFRA · APIS
modsem is grinding latent interaction models toward Mplus parity, one estimator at a time.
◆ Current state
modsem fits interaction and quadratic effects between latent variables in R, offering both product-indicator approaches (modsem_pi) and distribution-analytic ones (modsem_da, covering LMS and QML). Releases land roughly monthly and are dense pull-request lists. The recent line is dominated by the LMS approach: gradient refactors, parallel E-steps, composite construct support, and careful handling of residual covariances between latent variables.
◆ Where it's heading
Two things are being closed at once. The modelling gap — composites and formative constructs, categorical estimators, residual covariances in every direction, multigroup and clustered designs — brings modsem toward what commercial Mplus users expect, and the package's Mplus bridge is maintained alongside it, now with unique file IDs and a cleanup argument. The performance gap is the other: memoised H0, parallel E-step, optimized gradients and Hessians for both LMS and QML, all aimed at the distribution-analytic estimators that are expensive by construction. Convention borrowing from lavaan continues in message formatting and standard-error defaults.
◆ Prediction
The 1.0.20 and 1.0.21 releases both spent effort on residual covariances between endogenous and exogenous latent variables across estimation, prediction and standardization, and that thread has not obviously closed. The arrival of a second contributor moving MplusAutomation to Suggests suggests dependency trimming continues.
Alternatives to BAS and modsem
Other Infra & APIs products tracked by Sparkpulse, ranked by recent ship velocity. Each card links to a full editorial trajectory and lets you pivot into a head-to-head comparison with either BAS or modsem.
PINstimation
A market-microstructure toolkit that keeps adding estimators as the papers land.
nzilbb.vowels
A vowel-analysis package trimming dependencies after an email address got it archived.
emuR
The R half of the EMU speech database system, fixing what was quietly broken.
tidyplots
tidyplots keeps rebuilding its own foundations rather than layering around them.
GencoDymo2
A GENCODE annotation toolkit spent its first year getting out of CRAN's way.
Recent activity from BAS and modsem
Latest ship moves from both products, interleaved chronologically. ⚡ = editorial spark.
- 1mo agomodsemUnique Mplus file IDs, cleanup argument, LMS gradient refactor
- 2mo agomodsemComposite constructs for LMS, plus MC-LMS-CAT and MC-QML-CAT
- 3mo agomodsemPrint spacing and a partial-match fix in getSortedEtas()
- 4mo agomodsemCategorical argument for Mplus; partial support for the <~ operator
- 5mo agomodsemConsistent three-way interaction estimates with rcs=TRUE
- 6mo agomodsemSecondary pruning and a forward-difference Hessian mode
- 8mo agoBASBAS 2.0.2
- 8mo agoBASBAS 2.0.0
- 1y agoBASBAS 1.7.5
- 1y agoBASBAS 1.7.3
- 1y agoBASBAS 1.7.2
- 2y agoBASBAS 1.7.1
Frequently asked questions
What is the difference between BAS and modsem?
They serve adjacent needs but don't currently overlap on shipped themes. BAS and modsem are shipping at a similar cadence (velocity 0.0 vs 0.0, both within Sparkpulse's "active" band). See the at-a-glance table above for a side-by-side breakdown of velocity, recent sparks, and editorial themes.
Is BAS better than modsem?
Sparkpulse doesn't pick a winner — we score release velocity, not feature parity. BAS and modsem are shipping at a similar cadence (velocity 0.0 vs 0.0, both within Sparkpulse's "active" band). For your specific use case, the alternatives sections above list other Infra & APIs products to evaluate alongside.
What are the best alternatives to BAS?
Top BAS alternatives in Infra & APIs are ranked by recent ship velocity. Browse the "BAS alternatives" section above for the current picks, or visit /alternatives/bas for the full list with editorial commentary on each.
What are the best alternatives to modsem?
Top modsem alternatives in Infra & APIs are ranked by recent ship velocity. Browse the "modsem alternatives" section above for the current picks, or visit /alternatives/modsem for the full list with editorial commentary on each.