bayesfactor_models {bayestestR}R Documentation

Bayes Factors (BF) for model comparison

Description

This function computes or extracts Bayes factors from fitted models.

The bf_* function is an alias of the main function.

Usage

bayesfactor_models(..., denominator = 1, verbose = TRUE)

bf_models(..., denominator = 1, verbose = TRUE)

## S3 method for class 'bayesfactor_models'
update(object, subset = NULL, reference = NULL, ...)

## S3 method for class 'bayesfactor_models'
as.matrix(x, ...)

Arguments

...

Fitted models (see details), all fit on the same data, or a single BFBayesFactor object (see 'Details'). Ignored in as.matrix(), update().

denominator

Either an integer indicating which of the models to use as the denominator, or a model to be used as a denominator. Ignored for BFBayesFactor.

verbose

Toggle off warnings.

object, x

A bayesfactor_models object.

subset

Vector of model indices to keep or remove.

reference

Index of model to reference to, or "top" to reference to the best model, or "bottom" to reference to the worst model.

Details

If the passed models are supported by insight the DV of all models will be tested for equality (else this is assumed to be true), and the models' terms will be extracted (allowing for follow-up analysis with bayesfactor_inclusion).

In order to correctly and precisely estimate Bayes factors, a rule of thumb are the 4 P's: Proper Priors and Plentiful Posteriors. How many? The number of posterior samples needed for testing is substantially larger than for estimation (the default of 4000 samples may not be enough in many cases). A conservative rule of thumb is to obtain 10 times more samples than would be required for estimation (Gronau, Singmann, & Wagenmakers, 2017). If less than 40,000 samples are detected, bayesfactor_models() gives a warning.

See also the Bayes factors vignette.

Value

A data frame containing the models' formulas (reconstructed fixed and random effects) and their log(BF)s, that prints nicely.

Interpreting Bayes Factors

A Bayes factor greater than 1 can be interpreted as evidence against the null, at which one convention is that a Bayes factor greater than 3 can be considered as "substantial" evidence against the null (and vice versa, a Bayes factor smaller than 1/3 indicates substantial evidence in favor of the null-model) (Wetzels et al. 2011).

Note

There is also a plot()-method implemented in the see-package.

Author(s)

Mattan S. Ben-Shachar

References

Examples

# With lm objects:
# ----------------
lm1 <- lm(Sepal.Length ~ 1, data = iris)
lm2 <- lm(Sepal.Length ~ Species, data = iris)
lm3 <- lm(Sepal.Length ~ Species + Petal.Length, data = iris)
lm4 <- lm(Sepal.Length ~ Species * Petal.Length, data = iris)
bayesfactor_models(lm1, lm2, lm3, lm4, denominator = 1)
bayesfactor_models(lm2, lm3, lm4, denominator = lm1) # same result
BFM <- bayesfactor_models(lm1, lm2, lm3, lm4, denominator = lm1) # same result

update(BFM, reference = "bottom")
as.matrix(BFM)
## Not run: 
# With lmerMod objects:
# ---------------------
if (require("lme4")) {
  lmer1 <- lmer(Sepal.Length ~ Petal.Length + (1 | Species), data = iris)
  lmer2 <- lmer(Sepal.Length ~ Petal.Length + (Petal.Length | Species), data = iris)
  lmer3 <- lmer(
    Sepal.Length ~ Petal.Length + (Petal.Length | Species) + (1 | Petal.Width),
    data = iris
  )
  bayesfactor_models(lmer1, lmer2, lmer3, denominator = 1)
  bayesfactor_models(lmer1, lmer2, lmer3, denominator = lmer1)
}

# rstanarm models
# ---------------------
# (note that a unique diagnostic_file MUST be specified in order to work)
if (require("rstanarm")) {
  stan_m0 <- stan_glm(Sepal.Length ~ 1,
    data = iris,
    family = gaussian(),
    diagnostic_file = file.path(tempdir(), "df0.csv")
  )
  stan_m1 <- stan_glm(Sepal.Length ~ Species,
    data = iris,
    family = gaussian(),
    diagnostic_file = file.path(tempdir(), "df1.csv")
  )
  stan_m2 <- stan_glm(Sepal.Length ~ Species + Petal.Length,
    data = iris,
    family = gaussian(),
    diagnostic_file = file.path(tempdir(), "df2.csv")
  )
  bayesfactor_models(stan_m1, stan_m2, denominator = stan_m0)
}


# brms models
# --------------------
# (note the save_pars MUST be set to save_pars(all = TRUE) in order to work)
if (require("brms")) {
  brm1 <- brm(Sepal.Length ~ 1, data = iris, save_all_pars = TRUE)
  brm2 <- brm(Sepal.Length ~ Species, data = iris, save_all_pars = TRUE)
  brm3 <- brm(
    Sepal.Length ~ Species + Petal.Length,
    data = iris,
    save_pars = save_pars(all = TRUE)
  )

  bayesfactor_models(brm1, brm2, brm3, denominator = 1)
}


# BayesFactor
# ---------------------------
if (require("BayesFactor")) {
  data(puzzles)
  BF <- anovaBF(RT ~ shape * color + ID,
    data = puzzles,
    whichRandom = "ID", progress = FALSE
  )
  BF
  bayesfactor_models(BF) # basically the same
}

## End(Not run)

[Package bayestestR version 0.10.0 Index]