Manage Bibliography

Create, merge, and deduplicate BibTeX bibliography files using R. This skill covers the full lifecycle of bibliography management: parsing existing .bib files into structured R objects, generating new entries from identifiers (DOI, ISBN, arXiv ID), merging multiple bibliographies with intelligent deduplication, and exporting clean, consistently formatted .bib output.

When to Use

• Creating a new .bib file for an R Markdown or Quarto project
• Merging bibliographies from multiple collaborators or sources
• Deduplicating a .bib file that has grown through copy-paste accumulation
• Generating BibTeX entries programmatically from DOIs or other identifiers
• Cleaning and standardizing an existing .bib file (consistent keys, sorted fields)

Inputs

• Required: Path to one or more .bib files, or a list of DOIs/ISBNs/arXiv IDs
• Optional: Output .bib file path (default: references.bib)
• Optional: Deduplication strategy (doi, title, both; default: both)
• Optional: Sort order (author, year, key; default: key)
• Optional: Key generation pattern (default: AuthorYear)

Procedure

Step 1: Install and Load Required Packages

required_packages <- c("RefManageR", "bibtex", "stringdist")
missing <- required_packages[!vapply(required_packages, requireNamespace,
                                     logical(1), quietly = TRUE)]
if (length(missing) > 0) install.packages(missing)

library(RefManageR)

Expected: All packages load without errors.

On failure: If RefManageR fails to install, check that curl and xml2 system libraries are available. On Ubuntu: sudo apt install libcurl4-openssl-dev libxml2-dev.

Step 2: Parse Existing .bib Files

bib <- RefManageR::ReadBib("references.bib", check = FALSE)
message(sprintf("Parsed %d entries from references.bib", length(bib)))

# Inspect structure
print(bib[1:3])

# Access fields programmatically
keys <- names(bib)
years <- vapply(bib, function(x) x$year %||% NA_character_, character(1))

Expected: A BibEntry object containing all entries from the file. Entry count matches the number of @article{, @book{, etc. blocks in the file.

On failure: If parsing fails, check for unmatched braces or invalid UTF-8 in the .bib file. Run bibtex::read.bib() as a fallback with stricter parsing.

Step 3: Generate Entries from Identifiers

# From DOI
entry_doi <- RefManageR::GetBibEntryWithDOI("10.1093/bioinformatics/btz848")

# From a vector of DOIs
dois <- c("10.1093/bioinformatics/btz848", "10.1038/s41586-020-2649-2")
entries <- do.call(c, lapply(dois, function(d) {
  tryCatch(
    RefManageR::GetBibEntryWithDOI(d),
    error = function(e) {
      warning(sprintf("Failed to fetch DOI %s: %s", d, e$message))
      NULL
    }
  )
}))
entries <- Filter(Negate(is.null), entries)

Expected: BibEntry objects with complete metadata (title, author, journal, year, DOI) for each successfully resolved identifier.

On failure: DOI resolution depends on the CrossRef API. If requests fail, check network connectivity and whether the DOI is valid. Rate limiting may apply for large batches; add Sys.sleep(1) between requests.

Step 4: Merge Multiple Bibliographies

bib1 <- RefManageR::ReadBib("project_a.bib", check = FALSE)
bib2 <- RefManageR::ReadBib("project_b.bib", check = FALSE)

# Simple merge
merged <- c(bib1, bib2)
message(sprintf("Merged: %d + %d = %d entries (before dedup)",
                length(bib1), length(bib2), length(merged)))

Expected: A combined BibEntry object containing entries from both files.

Step 5: Deduplicate Entries

deduplicate_bib <- function(bib, method = "both") {
  n_before <- length(bib)
  keys_to_remove <- c()

  for (i in seq_along(bib)) {
    if (names(bib)[i] %in% keys_to_remove) next
    for (j in seq(i + 1, length(bib))) {
      if (j > length(bib)) break
      if (names(bib)[j] %in% keys_to_remove) next

      is_dup <- FALSE
      if (method %in% c("doi", "both")) {
        doi_i <- bib[[i]]$doi %||% ""
        doi_j <- bib[[j]]$doi %||% ""
        if (nzchar(doi_i) && nzchar(doi_j) && tolower(doi_i) == tolower(doi_j)) {
          is_dup <- TRUE
        }
      }
      if (!is_dup && method %in% c("title", "both")) {
        title_i <- tolower(gsub("[^a-z0-9 ]", "", tolower(bib[[i]]$title %||% "")))
        title_j <- tolower(gsub("[^a-z0-9 ]", "", tolower(bib[[j]]$title %||% "")))
        if (nzchar(title_i) && nzchar(title_j)) {
          sim <- 1 - stringdist::stringdist(title_i, title_j, method = "jw")
          if (sim > 0.95) is_dup <- TRUE
        }
      }
      if (is_dup) keys_to_remove <- c(keys_to_remove, names(bib)[j])
    }
  }

  if (length(keys_to_remove) > 0) {
    bib <- bib[!names(bib) %in% keys_to_remove]
  }
  message(sprintf("Deduplication: %d -> %d entries (%d duplicates removed)",
                  n_before, length(bib), n_before - length(bib)))
  bib
}

merged <- deduplicate_bib(merged, method = "both")

Expected: Duplicate entries removed. Count of removed duplicates printed.

On failure: If title comparison is too aggressive (removing non-duplicates), raise the similarity threshold above 0.95 or switch to method = "doi" only.

Step 6: Sort and Export

# Sort by citation key
sorted_bib <- sort(merged, sorting = "nyt")  # name-year-title

# Export to .bib file
RefManageR::WriteBib(sorted_bib, file = "references.bib", biblatex = FALSE)
message(sprintf("Wrote %d entries to references.bib", length(sorted_bib)))

Expected: A clean .bib file written to disk with consistent formatting, one entry per block, sorted alphabetically by citation key.

On failure: If WriteBib produces encoding issues, ensure the R session locale supports UTF-8: Sys.setlocale("LC_ALL", "en_US.UTF-8").

Validation

• Output .bib file parses without errors: RefManageR::ReadBib("references.bib")
• Entry count matches expectations (input count minus duplicates)
• No duplicate DOIs remain: all DOIs in output are unique
• All entries have a citation key
• Required fields present per entry type (author, title, year at minimum)
• File is valid BibTeX (test with bibtex::read.bib())

Common Pitfalls

• Encoding issues: .bib files with Latin-1 accents break UTF-8 parsers. Convert encoding first: iconv -f ISO-8859-1 -t UTF-8 old.bib > new.bib
• Unmatched braces: A single missing } silently drops entries. Validate brace balance before parsing large files
• DOI rate limiting: CrossRef throttles unauthenticated requests. Set a polite email with RefManageR::BibOptions(check.entries = FALSE) and batch requests
• Key collisions: Merging files with duplicate keys (e.g., both have Smith2020) silently overwrites. Regenerate keys after merging
• LaTeX in titles: Titles with {DNA} or $\alpha$ need careful handling; RefManageR preserves these but downstream tools may strip them

Related Skills

• format-citations - format the bibliography entries into styled citations
• validate-references - verify completeness and DOI resolution of .bib entries
• ../reporting/format-apa-report - generate APA-formatted reports using bibliographies
• ../r-packages/write-vignette - create package vignettes that cite references