fit_exp0: Fit exponential model without lag (EXP0)

In rumenGP: Rumen Gas Production Modeling, Comparison, and Visualization

Fit exponential model without lag (EXP0)

Description

Fits the exponential gas production model without an explicit lag phase.

Usage

fit_exp0(data, start = NULL)

Arguments

data	A rumen_gp object.
start	Optional list of starting values. May contain any of: Vf k

Details

Equation

V(t) = Vf \left( 1 - e^{-kt} \right)

where:

• V(t) is cumulative gas production at time t

• Vf is asymptotic gas production

• k is the fractional rate constant

Interpretation

The EXP0 model assumes that gas production increases exponentially toward an asymptotic value without an explicit lag phase.

Advantages

• Simple and computationally efficient

• Stable convergence

• Easy biological interpretation

Limitations

• Does not model lag time

• Limited flexibility for sigmoidal fermentation profiles

Value

An exp0_fit object containing:

• Parameter estimates

• Model diagnostics

• Predicted values

• Residuals

Examples

files <- example_data()

raw_data <- read_ankom(
  files$ankom
)

metadata <- read_metadata(
  files$metadata
)

gp <- process_ankom(
  raw_data,
  metadata,
  headspace_ml = 210,
  temperature_c = 39
)

# Fit using package defaults
fit_default <- fit_exp0(
  gp
)

summary(fit_default)

# Fit using user-defined starting values
fit_custom_start <- fit_exp0(
  gp,
  start = list(
    Vf = 120,
    k = 0.05
  )
)

summary(fit_custom_start)

rumenGP documentation built on Oct. 2, 2026, 5:09 p.m.