Check a data frame for alluvial structure

Alluvial diagrams consist of multiple horizontally-distributed columns (axes) representing factor variables, vertical divisions (strata) of these axes representing these variables' values; and splines (alluvial flows) connecting vertical subdivisions (lodes) within strata of adjacent axes representing subsets or amounts of observations that take the corresponding values of the corresponding variables. This function checks a data frame for either of two types of alluvial structure:

• One row per lode, wherein each row encodes a subset or amount of observations having a specific profile of axis values, a key field encodes the axis, a value field encodes the value within each axis, and a id column identifies multiple lodes corresponding to the same subset or amount of observations.

• One row per alluvium, wherein each row encodes a subset or amount of observations having a specific profile of axis values and a set axes of fields encodes its values at each axis variable.

If no arguments are assigned to any of these parameters, then is_alluvial will default to is_alluvial_alluvia and assume that all fields in data (other than weight, if given) are to be treated as axes.

is_alluvial(data, ..., logical = TRUE, silent = FALSE)

is_alluvial_lodes(data, key, value, id, weight = NULL, logical = TRUE,
  silent = FALSE)

is_alluvial_alluvia(data, axes, weight = NULL, logical = TRUE,
  silent = FALSE)

Arguments

data	A data frame.
...	Additional parameters used to determine method and passed thereto. All or none of key, value, and id, or else optionally axes, and (in either case) optionally weight.
logical	Whether to return a logical value (TRUE, the default) or a character string indicating the type of alluvial structure ("none", "lodes", or "alluvia")
silent	Whether to print warning messages.
key, value, id	Numeric or character; the fields of data corresponding to the axis (variable), stratum (value), and alluvium (identifying) variables.
weight	Optional numeric or character; the fields of data corresponding to alluvium or lode weights (heights when plotted).
axes	Numeric or character vector; the field(s) of data corresponding to the axi(e)s (variable(s)).

Examples

# Titanic data in alluvium form
titanic_alluvia <- as.data.frame(Titanic)
is_alluvial(titanic_alluvia,
            weight = "Freq")
#> [1] TRUE

# Titanic data in lode form
titanic_lodes <- suppressWarnings(tidyr::gather(
  dplyr::mutate(titanic_alluvia, Index = 1:nrow(titanic_alluvia)),
  "Variable", "Value", axes = 1:4, factor_key = TRUE
))
titanic_lodes$Value <- factor(titanic_lodes$Value,
                              levels = do.call(c, lapply(titanic_alluvia[, 1:4],
                                                         levels)))
is_alluvial(titanic_lodes,
            key = "Variable", value = "Value", id = "Index",
            weight = "Freq",
            logical = FALSE)
#> [1] "lodes"