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Pivot wide data to long for plotting as Sankey

Source: R/pivot_stages.r
pivot_stages_longer.Rd

Pivot data from a wide to a long format suitable for plotting Sankey diagrams.

Usage

pivot_stages_longer(
  data,
  stages_from,
  values_from,
  additional_aes_from,
  invert_nodes = FALSE
)

Arguments

data

A data.frame (or an object inheriting the data.frame class), which needs to be pivoted.

stages_from

A vector of column names, which represent the stages.

values_from

A vector of column names, which contains numeric values that represent the size of the edges in Sankey diagrams. When there are multiple values for a single edge, they are summed.

additional_aes_from

A vector of column names of data that you want to use to decorate elements in your Sankey diagram. This argument is optional. See also vignette("data_management") and vignette("decorating").

invert_nodes

When pivoting information from stages_from, its data is converted into a factor. Set invert_nodes to TRUE if you want to invert the order of the levels of the factor.

Value

Returns a dplyr::tibble with all the selected columns from data pivoted. The stages will be listed in the column named stage and nodes in the column named node. The result will contain two new columns: a column named connector indicating whether the row in the tibble reflects the source of an edge (value 'from') or destination of an edge (value 'to'); and a column named edge_id, containing a unique identifier for each edge. The edge_id is required for the plotting routine in order to identify which edge source should be connected with which edge destination.

Details

Typically, data to be displayed as a Sankey, is collected and stored in a wide format, where each stage (i.e., x-axis of a Sankey diagram) is in a column. The ggplot2 philosophy requires the data to be in a long format, such that diagram decorations (aesthetics) can be mapped to specific columns.

This function pivots wide data in an appropriate long format, by indicating which columns contain the stages, and in which order they should appear in the Sankey.

For more details see vignette("data_management")

Author

Pepijn de Vries

Examples

data("ecosystem_services")

ecosystem_services_p1 <-
  pivot_stages_longer(
    data        = ecosystem_services,
    stages_from = c("activity_type", "pressure_cat",
                    "biotic_group", "service_division"),
    values_from = "RCSES")

## suppose we want to decorate our Sankey
## with information on the 'section' of the services:
ecosystem_services_p2 <-
  pivot_stages_longer(
    data        = ecosystem_services,
    stages_from = c("activity_type", "pressure_cat",
                    "biotic_group", "service_division"),
    values_from = "RCSES",
    additional_aes_from = "service_section")