Example draws to use in demonstrations and tests

These functions return various objects containing data used in the examples throughout the bayesplot package documentation.

Usage

example_mcmc_draws(chains = 4, params = 4)

example_yrep_draws()

example_y_data()

example_x_data()

example_group_data()

Arguments

chains: An integer between 1 and 4 indicating the desired number of chains.
params: An integer between 1 and 6 indicating the desired number of parameters.

Value

See Details.

Details

Each of these functions returns an object containing data, parameter draws, or predictions corresponding to a basic linear regression model with data y (outcome vector) and X (predictor matrix), and parameters alpha (intercept), beta (coefficient vector), and sigma (error sd).

example_mcmc_draws(): If chains > 1, a 250 (iterations) by chains by params array or, if chains = 1, a 250 by params matrix of MCMC draws from the posterior distribution of the parameters in the linear regression model described above. If params = 1 then only the draws for alpha are included in the returned object. If params >= 2 then draws for sigma are also included. And if params is between 3 and the maximum of 6 then draws for regression coefficients beta[k] (k in 1:(params-2)) are also included.
example_y_data(): A numeric vector with 434 observations of the outcome variable in the linear regression model.
example_x_data(): A numeric vector with 434 observations of one of the predictor variables in the linear regression model.
example_group_data(): A factor variable with 434 observations of a grouping variable with two levels.
example_yrep_draws(): A 500 (draws) by 434 (data points) matrix of draws from the posterior predictive distribution. Each row represents a full dataset drawn from the posterior predictive distribution of the outcome y after fitting the linear regression model mentioned above.

Examples

draws <- example_mcmc_draws()
dim(draws)
#> [1] 250   4   4
dimnames(draws)
#> $Iteration
#> NULL
#> 
#> $Chain
#> [1] "chain:1" "chain:2" "chain:3" "chain:4"
#> 
#> $Parameter
#> [1] "alpha"   "sigma"   "beta[1]" "beta[2]"
#> 

draws <- example_mcmc_draws(1, 2)
dim(draws)
#> [1] 250   2
colnames(draws)
#> [1] "alpha" "sigma"

draws <- example_mcmc_draws(params = 6)
dimnames(draws)[[3]]
#> [1] "alpha"   "sigma"   "beta[1]" "beta[2]" "beta[3]" "beta[4]"

y <- example_y_data()
x <- example_x_data()
group <- example_group_data()
length(y)
#> [1] 434
length(x)
#> [1] 434
length(group)
#> [1] 434
tail(data.frame(y, x, group), 5)
#>      y        x  group
#> 430 94 84.87741 GroupA
#> 431 76 92.99039 GroupB
#> 432 50 94.85971 GroupA
#> 433 88 96.85662 GroupB
#> 434 70 91.25334 GroupB

yrep <- example_yrep_draws()
dim(yrep) # ncol(yrep) = length(y) = length(x) = length(group)
#> [1] 500 434