Extract parameter draws from a model object

This function helps the user extract relevant estimates from parameters fit using a Bayesian Bradley-Terry model.

Usage

parameter(model_output, parameter_name, indices_to_extract = NULL)

Arguments

model_output: The mcmc object that contains the draws output from the BBT model.
parameter_name: The name of the parameter to extract draws for.
indices_to_extract: A single column index or a vector of column indices to extract from the draws matrix.

Value

A vector containing the draws of the parameter.

Examples


prior.var <- expm::expm(forcedMarriage$adjacencyMatrix)
prior.var <- diag(diag(prior.var)^-0.5) %*% prior.var %*% diag(diag(prior.var)^-0.5)

# Fit model
# Using `n.iter = 3, burn.in = 0` to reduce runtime
# - you should use more iterations for reliable posterior estimates
forcedMarriageModel <- speedyBBTm(
  outcome = rep(1, length(forcedMarriage$comparisons$win)),
  player1 = forcedMarriage$comparisons$win,
  player2 = forcedMarriage$comparisons$lost,
  player.prior.var = prior.var, n.iter = 3, burn.in = 0
)

parameter(forcedMarriageModel, "lambda", c(10, 20, 30, 40))
#> Markov Chain Monte Carlo (MCMC) output:
#> Start = 1 
#> End = 3 
#> Thinning interval = 1 
#>       lambda[10] lambda[20]   lambda[30] lambda[40]
#> [1,] -0.04308484 0.03583124  0.005005878 0.03808586
#> [2,] -0.08989272 0.09774010 -0.039271672 0.09039862
#> [3,] -0.06606301 0.17611285 -0.010403523 0.09373349
parameter(forcedMarriageModel, "alpha.sq")
#> Markov Chain Monte Carlo (MCMC) output:
#> Start = 1 
#> End = 3 
#> Thinning interval = 1 
#>          alpha.sq
#> [1,] 0.0002800973
#> [2,] 0.0005409323
#> [3,] 0.0011879260