parse_dist function

Parse distribution specifications into columns of a data frame

Parses simple string distribution specifications, like "normal(0, 1)", into two columns of a data frame, suitable for use with the dist and args aesthetics of stat_slabinterval()

and its shortcut stats (like stat_halfeye()). This format is output by brms::get_prior, making it particularly useful for visualizing priors from brms models.

parse_dist(
  object,
  ...,
  dist = ".dist",
  args = ".args",
  dist_obj = ".dist_obj",
  package = NULL,
  to_r_names = TRUE
)

## Default S3 method:
parse_dist(object, ...)

## S3 method for class 'data.frame'
parse_dist(
  object,
  dist_col,
  ...,
  dist = ".dist",
  args = ".args",
  dist_obj = ".dist_obj",
  package = NULL,
  lb = "lb",
  ub = "ub",
  to_r_names = TRUE
)

## S3 method for class 'character'
parse_dist(
  object,
  ...,
  dist = ".dist",
  args = ".args",
  dist_obj = ".dist_obj",
  package = NULL,
  to_r_names = TRUE
)

## S3 method for class 'factor'
parse_dist(
  object,
  ...,
  dist = ".dist",
  args = ".args",
  dist_obj = ".dist_obj",
  package = NULL,
  to_r_names = TRUE
)

## S3 method for class 'brmsprior'
parse_dist(
  object,
  dist_col = prior,
  ...,
  dist = ".dist",
  args = ".args",
  dist_obj = ".dist_obj",
  package = NULL,
  to_r_names = TRUE
)

r_dist_name(dist_name)

Arguments

• object: A character vector containing distribution specifications or a data frame with a column containing distribution specifications.

• ...: Arguments passed to other implementations of parse_dist.

• dist: The name of the output column to contain the distribution name

• args: The name of the output column to contain the arguments to the distribution

• dist_obj: The name of the output column to contain a distributional object representing the distribution

• package: The package or environment to search for distribution functions in. Passed to distributional::dist_wrap(). One of:

  • NULL: use the calling environment
  • a string: use the environment for the package with the given name
  • an environment : use the given environment

• to_r_names: If TRUE (the default), certain common aliases for distribution names are automatically translated into names that R can recognize (i.e., names which have functions starting with r, p, q, and d representing random number generators, distribution functions, etc. for that distribution), using the r_dist_name function. For example, "normal" is translated into "norm" and "lognormal" is translated into "lnorm".

• dist_col: A bare (unquoted) column or column expression that resolves to a character vector of distribution specifications.

• lb: The name of an input column (for data.frame and brms::prior objects) that contains the lower bound of the distribution, which if present will produce a truncated distribution using dist_truncated(). Ignored if lb is NULL or if object[[lb]] is NA for the corresponding input row.

• ub: The name of an input column (for data.frame and brms::prior objects) that contains the upper bound of the distribution, which if present will produce a truncated distribution using dist_truncated(). Ignored if ub is NULL or if object[[ub]] is NA for the corresponding input row.

• dist_name: For r_dist_name, a character vector of distribution names to be translated into distribution names R recognizes. Unrecognized names are left as-is.

Returns

• parse_dist returns a data frame containing at least two columns named after the dist and args

  parameters. If the input is a data frame, the output is a data frame of the same length with those two columns added. If the input is a character vector or factor, the output is a two-column data frame with the same number of rows as the length of the input.

• r_dist_name returns a character vector the same length as the input containing translations of the input names into distribution names R can recognize.

Details

parse_dist() can be applied to character vectors or to a data frame + bare column name of the column to parse, and returns a data frame with ".dist" and ".args" columns added. parse_dist() uses r_dist_name() to translate distribution names into names recognized by R.

r_dist_name() takes a character vector of names and translates common names into R distribution names. Names are first made into valid R names using make.names(), then translated (ignoring character case, ".", and "_"). Thus, "lognormal", "LogNormal", "log_normal", "log-Normal", and any number of other variants all get translated into "lnorm".

Examples

library(dplyr)

# parse dist can operate on strings directly...
parse_dist(c("normal(0,1)", "student_t(3,0,1)"))

# ... or on columns of a data frame, where it adds the
# parsed specs back on as columns
data.frame(prior = c("normal(0,1)", "student_t(3,0,1)")) %>%
  parse_dist(prior)

# parse_dist is particularly useful with the output of brms::prior(),
# which follows the same format as above

See Also

See stat_slabinterval() and its shortcut stats, which can easily make use of the output of this function using the dist and args aesthetics.