R: Histograms and kernel density plots of MCMC draws

MCMC-distributions {bayesplot}

R Documentation

Histograms and kernel density plots of MCMC draws

Description

Various types of histograms and kernel density plots of MCMC draws. See the Plot Descriptions section, below, for details.

Usage

mcmc_hist(x, pars = character(), regex_pars = character(),
  transformations = list(), facet_args = list(), ..., binwidth = NULL,
  freq = TRUE)

mcmc_dens(x, pars = character(), regex_pars = character(),
  transformations = list(), facet_args = list(), ..., trim = FALSE)

mcmc_hist_by_chain(x, pars = character(), regex_pars = character(),
  transformations = list(), facet_args = list(), ..., binwidth = NULL,
  freq = TRUE)

mcmc_dens_overlay(x, pars = character(), regex_pars = character(),
  transformations = list(), facet_args = list(), ..., trim = FALSE)

mcmc_violin(x, pars = character(), regex_pars = character(),
  transformations = list(), facet_args = list(), ..., probs = c(0.1, 0.5,
  0.9))

Arguments

`x`	A 3-D array, matrix, list of matrices, or data frame of MCMC draws. The MCMC-overview page provides details on how to specify each these allowed inputs.
`pars`	An optional character vector of parameter names. If neither `pars` nor `regex_pars` is specified then the default is to use all parameters.
`regex_pars`	An optional regular expression to use for parameter selection. Can be specified instead of `pars` or in addition to `pars`.
`transformations`	Optionally, transformations to apply to parameters before plotting. If `transformations` is a function or a single string naming a function then that function will be used to transform all parameters. To apply transformations to particular parameters, the `transformations` argument can be a named list with length equal to the number of parameters to be transformed. Currently only univariate transformations of scalar parameters can be specified (multivariate transformations will be implemented in a future release). If `transformations` is a list, the name of each list element should be a parameter name and the content of each list element should be a function (or any item to match as a function via `match.fun`, e.g. a string naming a function). If a function is specified by its name as a string (e.g. `"log"`), then it can be used to construct a new parameter label for the appropriate parameter (e.g. `"log(sigma)"`). If a function itself is specified (e.g. `log` or `function(x) log(x)`) then `"t"` is used in the new parameter label to indicate that the parameter is transformed (e.g. `"t(sigma)"`).
`facet_args`	A named list of arguments (other than `facets`) passed to `facet_wrap` or `facet_grid` to control faceting.
`...`	Currently ignored.
`binwidth`	An optional value used as the `binwidth` argument to `geom_histogram` to override the default binwidth.
`freq`	For histograms, `freq=TRUE` (the default) puts count on the y-axis. Setting `freq=FALSE` puts density on the y-axis. (For many plots the y-axis text is off by default. To view the count or density labels on the y-axis see the `yaxis_text` convenience function.)
`trim`	A logical scalar passed to `geom_density`.
`probs`	A numeric vector passed to `geom_violin`'s `draw_quantiles` argument to specify at which quantiles to draw horizontal lines. Set to `NULL` to remove the lines.

Value

A ggplot object that can be further customized using the ggplot2 package.

Plot Descriptions

mcmc_hist: Histograms of posterior draws with all chains merged.
mcmc_dens: Kernel density plots of posterior draws with all chains merged.
mcmc_hist_by_chain: Histograms of posterior draws with chains separated via faceting.
mcmc_dens_overlay: Kernel density plots of posterior draws with chains separated but overlaid on a single plot.
mcmc_violin: The density estimate of each chain is plotted as a violin with horizontal lines at notable quantiles.

Examples

# some parameter draws to use for demonstration
x <- example_mcmc_draws()
dim(x)
dimnames(x)

##################
### Histograms ###
##################

# histograms of all parameters
color_scheme_set("brightblue")
mcmc_hist(x)

# histograms of some parameters
color_scheme_set("pink")
mcmc_hist(x, pars = c("alpha", "beta[2]"))

mcmc_hist(x, pars = "sigma", regex_pars = "beta")

# example of using 'transformations' argument to plot log(sigma),
# and parsing facet labels (e.g. to get greek letters for parameters)
mcmc_hist(x, transformations = list(sigma = "log"),
          facet_args = list(labeller = ggplot2::label_parsed)) +
          facet_text(size = 15)

# instead of list(sigma = "log"), you could specify the transformation as
# list(sigma = log) or list(sigma = function(x) log(x)), but then the
# label for the transformed sigma is 't(sigma)' instead of 'log(sigma)'
mcmc_hist(x, transformations = list(sigma = log))

# separate histograms by chain
color_scheme_set("pink")
mcmc_hist_by_chain(x, regex_pars = "beta")

#################
### Densities ###
#################

mcmc_dens(x, pars = c("sigma", "beta[2]"),
          facet_args = list(nrow = 2))

# separate and overlay chains
color_scheme_set("mix-teal-pink")
mcmc_dens_overlay(x, pars = c("sigma", "beta[2]"),
                  facet_args = list(nrow = 2)) +
                  facet_text(size = 14)

# separate chains as violin plots
color_scheme_set("green")
mcmc_violin(x) + panel_bg(color = "gray20", size = 2, fill = "gray30")

[Package bayesplot version 1.4.0 Index]