resolve_redirects: Resolve Redirects in an Edge List

In pagerankr: Modular Toolkit for PageRank Calculation

Resolve Redirects in an Edge List

Description

Updates an edge list by replacing URLs with their final destinations based on a redirect data frame. Handles redirect chains, detects cycles, and resolves conflicting redirects using configurable policies.

Usage

resolve_redirects(
  edge_list_df,
  redirects_df,
  edge_from_col = "from",
  edge_to_col = "to",
  redirect_from_col = "from",
  redirect_to_col = "to",
  duplicate_from_policy = c("strict", "first_wins", "last_wins", "most_frequent",
    "prune_source", "resolve_if_consistent"),
  loop_handling = c("error", "prune_loop", "break_arrow")
)

Arguments

edge_list_df	A data frame representing the edge list.
redirects_df	A data frame containing redirect rules, with 'from' and 'to' columns specifying the source and target of a redirect.
edge_from_col	Character, the name of the column in 'edge_list_df' containing source URLs. Default "from".
edge_to_col	Character, the name of the column in 'edge_list_df' containing target URLs. Default "to".
redirect_from_col	Character, the name of the column in 'redirects_df' containing source URLs of redirects. Default "from".
redirect_to_col	Character, the name of the column in 'redirects_df' containing target URLs of redirects. Default "to".
duplicate_from_policy	Character, how to handle conflicting redirects (same source URL mapping to multiple distinct targets). One of: "strict" (Default) Error on any conflict. "first_wins" Keep the first occurrence for each conflicting source. "last_wins" Keep the last occurrence for each conflicting source. "most_frequent" Keep the most common target. Ties broken by first occurrence. "prune_source" Remove ALL redirects from any conflicting source. "resolve_if_consistent" Allow exact duplicates; error only on true conflicts where targets differ.
loop_handling	Character, how to handle redirect cycles (loops). One of: "error" (Default) Error when a redirect cycle is detected. "prune_loop" Remove all edges involved in cycles. URLs in the loop remain unresolved (map to themselves). "break_arrow" For each cycle, keep the node with the highest in-degree as the sink and remove edges pointing away from it within the cycle. This preserves as much of the chain as possible.

Details

Self-referencing redirects (where from == to) and any redirects with NA in from or to are automatically filtered out before processing.

When crawl data contains conflicting redirects (the same URL redirecting to different targets), use duplicate_from_policy to control the behavior. The default "strict" preserves backward compatibility by erroring on any conflict.

Redirect resolution uses a graph-based approach: an igraph is built from the redirect rules, strongly connected components (SCCs) are used to detect loops, and the loop_handling policy determines what happens to cycles. After loop handling, each URL is mapped to its terminal destination by traversing the acyclic graph.

Value

An updated 'edge_list_df' with URLs in 'edge_from_col' and 'edge_to_col' replaced by their final resolved destinations.

See Also

Other edge-list resolvers: resolve_canonicals(), resolve_links()

Examples

edges <- data.frame(
  from = c("A", "B", "C"),
  to = c("B", "C", "D")
)
redirects <- data.frame(
  from = c("B", "C", "E"),
  to = c("B_final", "C_final", "E_final")
)
resolve_redirects(edges, redirects)

# Example with a redirect chain
edges_chain <- data.frame(from = "X", to = "Y")
redirects_chain <- data.frame(
  from = c("Y", "Z"),
  to = c("Z", "Z_final")
)
resolve_redirects(edges_chain, redirects_chain)

# Example with conflicting redirects resolved via first_wins
edges_conflict <- data.frame(
  from = "A", to = "B"
)
redirects_conflict <- data.frame(
  from = c("B", "B"),
  to = c("C", "D")
)
resolve_redirects(edges_conflict, redirects_conflict,
  duplicate_from_policy = "first_wins"
)

# Example with different column names
edges_custom <- data.frame(
  source_url = "Page1", target_url = "Page2"
)
redirects_custom <- data.frame(
  original = "Page2", final = "Page2_resolved"
)
resolve_redirects(edges_custom, redirects_custom,
  edge_from_col = "source_url",
  edge_to_col = "target_url",
  redirect_from_col = "original",
  redirect_to_col = "final"
)

pagerankr documentation built on Oct. 1, 2026, 5:09 p.m.