blavFitIndices {blavaan}

SEM Fit Indices for Bayesian SEM

Description

This function provides a posterior distribution of some \chi^2-based fit indices to assess the global fit of a latent variable model.

Usage

blavFitIndices(object, thin = 1L, pD = c("loo","waic","dic"),
               rescale = c("devM","ppmc","mcmc"),
               fit.measures = "all", baseline.model = NULL)

## S4 method for signature 'blavFitIndices'
## S4 method for signature 'blavFitIndices'
summary(object, ...)

## S3 method for class 'bfi'
summary(object, central.tendency = c("mean","median","mode"),
        hpd = TRUE, prob = .90)

Arguments

object

An object of class blavaan.

thin

Optional integer indicating how much to thin each chain. Default is 1L, indicating not to thin the chains.

pD

character indicating from which information criterion returned by fitMeasures(object) to use the estimated number of parameters. The default is from the leave-one-out information criterion (LOO-IC), which is most highly recommended by Vehtari et al. (2017).

rescale

character indicating the method used to calculate fit indices. If rescale = "devM" (default), the Bayesian analog of the \chi^2 statistic (the deviance evaluated at the posterior mean of the model parameters) is approximated by rescaling the deviance at each iteration by subtracting the estimated number of parameters. If rescale = "PPMC", the deviance at each iteration is rescaled by subtracting the deviance of data simulated from the posterior predictive distribution (as in posterior predictive model checking; see Hoofs et al., 2017). If rescale = "MCMC", the fit measures are simply calculated using fitMeasures at each iteration of the Markov chain(s), based on the model-implied moments at that iteration (NOT advised when the model includes informative priors, in which case the model's estimated pD will deviate from the number of parameters used to calculate df in fitMeasures).

fit.measures

If "all", all fit measures available will be returned. If only a single or a few fit measures are specified by name, only those are computed and returned. If rescale = "devM" or "PPMC", the currently available indices are "BRMSEA", "BGammaHat", "adjBGammaHat", "BMc", "BCFI", "BTLI", or "BNFI". If rescale = "MCMC", the user may request any indices returned by fitMeasures for objects of class lavaan.

baseline.model

If not NULL, an object of class blavaan, representing a user-specified baseline model. If a baseline.model is provided, incremental fit indices (BCFI, BTLI, or BNFI) can be requested in fit.measures. Ignored if rescale = "MCMC".

...

Additional arguments to the summary method:

central.tendency

Takes values "mean", "median", "mode", indicating which statistics should be used to characterize the location of the posterior distribution. By default, all 3 statistics are returned. The posterior mean is labeled EAP for expected a posteriori estimate, and the mode is labeled MAP for modal a posteriori estimate.

hpd

A logical indicating whether to calculate the highest posterior density (HPD) credible interval for each fit index (defaults to TRUE).

prob

The "confidence" level of the credible interval(s) (defaults to 0.9).

Value

An S4 object of class blavFitIndices consisting of 2 slots:

@details

A list containing the choices made by the user (or defaults; e.g., which values of pD and rescale were set), as well as the posterior distribution of the \chi^2 (deviance) statistic (rescaled, if rescale = "devM" or "PPMC").

@indices

A list containing the posterior distribution of each requested fit.measure.

The summary() method returns a data.frame containing one row for each requested fit.measure, and columns containing the specified measure(s) of central.tendency, the posterior SD, and (if requested) the HPD credible-interval limits.

Author(s)

Mauricio Garnier-Villareal (Vrije Universiteit Amsterdam; [e-mail])

Terrence D. Jorgensen (University of Amsterdam; [e-mail])

References

rescale = "PPMC" based on:

Hoofs, H., van de Schoot, R., Jansen, N. W., & Kant, I. (2017). Evaluating model fit in Bayesian confirmatory factor analysis with large samples: Simulation study introducing the BRMSEA. Educational and Psychological Measurement. doi:10.1177/0013164417709314

rescale = "devM" based on:

Garnier-Villarreal, M., & Jorgensen, T. D. (2020). Adapting Fit Indices for Bayesian Structural Equation Modeling: Comparison to Maximum Likelihood. Psychological Methods, 25(1), 46–70. https://doi.org/dx.doi.org/10.1037/met0000224 (See also https://osf.io/afkcw/)

Other references:

Vehtari, A., Gelman, A., & Gabry, J. (2017). Practical Bayesian model evaluation using leave-one-out cross-validation and WAIC. Statistics and Computing, 27(5), 1413–1432. doi:10.1007/s11222-016-9696-4

Examples

 ## Not run: 
data(HolzingerSwineford1939, package = "lavaan")

HS.model <- ' visual  =~ x1 + x2 + x3
              textual =~ x4 + x5 + x6
              speed   =~ x7 + x8 + x9 '
## fit target model
fit1 <- bcfa(HS.model, data = HolzingerSwineford1939, 
             n.chains = 2, burnin = 1000, sample = 1000)

## fit null model to calculate CFI, TLI, and NFI
null.model <- c(paste0("x", 1:9, " ~~ x", 1:9), paste0("x", 1:9, " ~ 1"))
fit0 <- bcfa(null.model, data = HolzingerSwineford1939, 
             n.chains = 2, burnin = 1000, sample = 1000)

## calculate posterior distributions of fit indices

## The default method mimics fit indices derived from ML estimation
ML <- blavFitIndices(fit1, baseline.model = fit0)
ML
summary(ML)

## other options:

## - use Hoofs et al.'s (2017) PPMC-based method
## - use the estimated number of parameters from WAIC instead of LOO-IC
PPMC <- blavFitIndices(fit1, baseline.model = fit0,
                       pD = "waic", rescale = "PPMC")
## issues a warning about using rescale="PPMC" with N < 1000 (see Hoofs et al.)

## - specify only the desired measures of central tendency
## - specify a different "confidence" level for the credible intervals
summary(PPMC, central.tendency = c("mean","mode"), prob = .95)



## Access the posterior distributions for further investigation
head(distML <- data.frame(ML@indices))

## For example, diagnostic plots using the bayesplot package:

## distinguish chains
nChains <- blavInspect(fit1, "n.chains")
distML$Chain <- rep(1:nChains, each = nrow(distML) / nChains)

library(bayesplot)
mcmc_pairs(distML, pars = c("BRMSEA","BMc","BGammaHat","BCFI","BTLI"),
           diag_fun = "hist")
## Indices are highly correlated across iterations in both chains

## Compare to PPMC method
distPPMC <- data.frame(PPMC@indices)
distPPMC$Chain <- rep(1:nChains, each = nrow(distPPMC) / nChains)
mcmc_pairs(distPPMC, pars = c("BRMSEA","BMc","BGammaHat","BCFI","BTLI"),
           diag_fun = "dens")
## nonlinear relation between BRMSEA, related to the floor effect of BRMSEA
## that Hoofs et al. found for larger (12-indicator) models


## End(Not run)