NEWS

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rumenGP 0.2.1 (2026-10-07)

New Models

Added two new nonlinear gas production models:

• Burr XII
• Inverse Paralogistic

Burr XII

Equation:

V(t) = VF [1 - (1 + (rt)^a)^(-p)]

Features:

• Flexible four-parameter sigmoidal model
• Accommodates diverse fermentation profiles
• Supports asymmetry and variable inflection behavior
• Useful for comparative model-selection studies

Inverse Paralogistic

Equation:

V(t) = VF [1 + (rt)^(-a)]^(-a)

Features:

• Flexible three-parameter sigmoidal model
• Biologically interpretable asymptote
• Strong performance across diverse fermentation profiles

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Documentation Improvements

Model Reference Vignette

Updated the "Model Equations Reference" vignette:

• Added Burr XII documentation
• Added Inverse Paralogistic documentation
• Added model-selection guidance
• Expanded model-equivalence discussion

Model Interpretation Vignette

Updated the "Interpreting Gas Production Models" vignette:

• Added interpretation of Burr XII parameters
• Added interpretation of Inverse Paralogistic parameters
• Expanded discussion of shape parameters
• Added model-equivalence interpretation
• Added practical model-selection guidance

Getting Started Vignette

Updated the "Getting Started with rumenGP" vignette:

• Added Burr XII examples
• Added Inverse Paralogistic examples
• Expanded model-comparison workflow
• Added model-selection recommendations

Importing Non-ANKOM Data Vignette

Updated the "Importing Non-ANKOM Data" vignette:

• Added examples using newly implemented models
• Expanded model-comparison examples
• Added model-equivalence notes

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Model Equivalence Documentation

Documented the mathematical equivalence of:

• Groot
• Generalized Michaelis-Menten
• Log-logistic

Parameter correspondence:

• VF = A = VF
• b = K = 1/r
• k = c = a

Clarified that these models represent mathematically equivalent parameterizations of the same underlying sigmoidal gas-production curve for positive values of time.

Documented differences in the handling of time-zero observations, including the exclusion of Time_h = 0 when fitting the Groot model because the formulation is undefined at (t = 0), and the retention of time-zero observations in the Generalized Michaelis-Menten and Log-logistic formulations.

rumenGP now implements all three parameterizations, allowing researchers to select the formulation most appropriate for their field while recognizing their underlying mathematical equivalence.

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README Improvements

Updated package documentation:

• Added Burr XII
• Added Inverse Paralogistic
• Documented model equivalence
• Expanded model-comparison examples
• Added recommended model-selection workflow
• Updated built-in model count

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Package Content

Current built-in model library:

• Brody
• Burr XII
• Dual Logistic
• EXP0
• EXPL
• Generalized Michaelis-Menten
• Gompertz
• Groot
• Inverse Paralogistic
• LE0
• LEL
• Logistic
• Log-logistic
• Mitscherlich
• Ørskov and McDonald

Total:

• 15 built-in kinetic models

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Quality Assurance

• Updated package documentation throughout
• Updated package website content
• Updated vignettes
• Updated examples
• Maintained clean package checks

R CMD check:

• 0 errors
• 0 warnings
• 0 notes