toFile: Write or read a Markov chain to or from a file

In markovchain: Easy Handling Discrete Time Markov Chains

Write or read a Markov chain to or from a file

Description

Writes a markovchain object to a JSON, YAML, CSV or XML file, or reads one back, using the same representation as toDictionary.

Usage

toFile(object, file, format = NULL)

## S4 method for signature 'markovchain'
toFile(object, file, format = NULL)

fromFile(file, format = NULL)

Arguments

object	A markovchain object (for toFile).
file	A single file path to write to or read from. If format is not supplied, it is inferred from the file extension (.json, .yaml/.yml, .csv or .xml).
format	One of "json", "yaml", "csv" or "xml". The default, NULL, infers the format from file's extension.

Details

The JSON and YAML formats store exactly what toDictionary returns (name, state names, and the transition probabilities nested by source state), and round-trip a chain exactly, including full numeric precision (toFile writes both JSON and YAML with 17 significant digits, enough to recover every double exactly).

The CSV format only stores the transition matrix itself, as a table of probabilities with the state names as both the header row and the first column – there is no natural place in a CSV file for the chain's name, so it is not preserved by toFile(..., format = "csv") and fromFile always returns an unnamed chain for a .csv file. This is the same limitation PyDTMC's own CSV format has.

The XML format is the one of PyDTMC, so files can be exchanged with it in both directions: a root element MarkovChain with one Item element per transition, whose attributes are state_from, state_to and probability. All n^2 transitions are written, zeros included, and probabilities use 17 significant digits, so the round trip is exact. The name of the chain is stored as an attribute of the root element, which PyDTMC ignores when reading. When reading, the states are taken in the order in which their self transitions (state_from equal to state_to) appear, as PyDTMC does, and the name is restored if the attribute is present. Writing XML uses only base R; reading it requires the xml2 package.

Writing JSON requires the jsonlite package, and writing YAML requires the yaml package; both are only in Suggests, and an informative error is raised if the relevant package is not installed. Reading has the same requirements for the format being read. CSV uses only base R and has no extra package dependency.

Value

toFile returns file, invisibly. fromFile returns a markovchain object.

See Also

toDictionary, fromDictionary

Examples

## Not run: 
statesNames <- c("a", "b")
mc <- new("markovchain", states = statesNames,
          transitionMatrix = matrix(c(0.7, 0.3, 0.4, 0.6), byrow = TRUE,
                                     nrow = 2, dimnames = list(statesNames, statesNames)))
toFile(mc, "chain.json")
identical(fromFile("chain.json")@transitionMatrix, mc@transitionMatrix)

## End(Not run)

markovchain documentation built on Oct. 10, 2026, 9:07 a.m.