combine_chains {tidybayes}

Combine the chain and iteration columns of tidy data frames of draws

Description

Combines the chain and iteration columns of a tidy data frame of draws from a Bayesian model fit into a new column that can uniquely identify each draw. Generally speaking not needed for pure tidybayes code, as tidybayes functions now automatically include a .draw column, but can be useful when interacting with packages that do not provide such a column.

Usage

combine_chains(data, chain = .chain, iteration = .iteration, into = ".draw")

Arguments

data

Tidy data frame of draws with columns representing the chain and iteration of each draw.

chain

Bare name of column in data indicating the chain of each row. The default (.chain) is the same as used by other functions in tidybayes.

iteration

Bare name of column in data indicating the iteration of each row. The default (.iteration) is the same as used by other functions in tidybayes.

into

Name (as a character vector) of the column to combine chains into. The default, NULL, replaces the chain column with NAs and writes the combined chain iteration numbers into iteration. If provided, chain and iteration will not be modified, and the combined iteration number will be written into a new column named into.

Value

A data frame of tidy draws with a combined iteration column

Author(s)

Matthew Kay

See Also

emmeans::emmeans()

Examples

library(magrittr)
library(coda)

data(line, package = "coda")

# The `line` posterior has two chains with 200 iterations each:
line %>%
  tidy_draws() %>%
  summary()

# combine_chains combines the chain and iteration column into the .draw column.
line %>%
  tidy_draws() %>%
  combine_chains() %>%
  summary()