Contrasts Between Ratio Conditions — ratio

Compute posterior distributions of contrasts (differences or ratios) between conditions for the derived ratio quantity.

Usage

ratio_contrast(
  object,
  contrast,
  type = c("difference", "ratio"),
  ref = NULL,
  ...
)

# S3 method for class 'ratiod_contrast'
print(x, ...)

Arguments

object: A ratiod_fit object
contrast: A formula specifying the contrast, e.g., ~ treatment
type: Type of contrast: "difference" (default) or "ratio"
ref: Reference level for factor contrasts (default: first level)
...: Ignored
x: A ratiod_contrast object

Value

A data frame with posterior summaries of contrasts

Examples

# \donttest{
# Generate synthetic data with grouping variable
set.seed(456)
n <- 60
df <- data.frame(
  count = rpois(n, lambda = 25),
  effort = rgamma(n, shape = 12, rate = 1),
  season = sample(c("summer", "winter"), n, replace = TRUE)
)

# Fit model
fit <- tratio(
  count | effort ~ season,
  data = df,
  family = ratiod_poisson_gamma(),
  mode = "hmc",
  control = list(iter = 400, chains = 1, seed = 1)
)

# Compare CPUE between seasons
ratio_contrast(fit, ~ season)
#> tulpaRatio ratio contrasts
#> =====================
#> 
#> Type: difference 
#> Variable: season 
#> Reference: summer 
#> 
#>          contrast      mean         sd       q2.5        q50      q97.5
#>  winter vs summer -0.123931 0.08549462 -0.2502178 -0.1269074 0.08390861
#>  prob_positive
#>           0.08

# Ratio of ratios (multiplicative comparison)
ratio_contrast(fit, ~ season, type = "ratio")
#> tulpaRatio ratio contrasts
#> =====================
#> 
#> Type: ratio 
#> Variable: season 
#> Reference: summer 
#> 
#>          contrast      mean        sd      q2.5       q50   q97.5 prob_positive
#>  winter vs summer 0.8866986 0.0773782 0.7786313 0.8808152 1.08753             1
# }