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Compute the Adjacency Matrix for a vector of preferences

Source: R/adjacency.R
adjacency.Rd

Convert a set of preferences to an adjacency matrix summarising wins and losses between pairs of items.

Usage

adjacency(x, preferences_col = NULL, frequency_col = NULL, ...)

Arguments

x

A preferences object or a tibble with a preferences-typed column.

preferences_col

<tidy-select> When x is a tibble, the column containing the preferences.

frequency_col

<tidy-select> When x is a tibble, the column containing the frequency of the preferences. If not provided, each row is considered to be observed a single time.

...

Currently unused.

Value

An \(N\) by \(N\) matrix, where \(N\) is the number of items.

Details

For a preferences object with \(N\) items, the adjacency matrix is an \(N\) by \(N\) matrix, with element \((i, j)\) being the number of times item \(i\) wins over item \(j\). For example, in the preferences {1} > {3, 4} > {2}, item 1 wins over items 2, 3, and 4, while items 3 and 4 win over item 2.

If weights is specified, the values in the adjacency matrix are the weighted counts.

Examples

x <- tibble::tribble(
  ~voter_id, ~species, ~food, ~ranking,
  1, "Rabbit", "Apple", 1,
  1, "Rabbit", "Banana", 2,
  1, "Rabbit", "Carrot", 3,
  2, "Monkey", "Banana", 1,
  2, "Monkey", "Apple", 2,
  2, "Monkey", "Carrot", 3
) |>
  long_preferences(
    food_preference,
    id_cols = voter_id,
    item_col = food,
    rank_col = ranking
  ) |>
  dplyr::pull(food_preference) |>
  adjacency()