Getting started with scholidonline

Installation

install.packages("scholidonline")

Interface

scholidonline exposes a small set of user-facing functions:

• scholidonline_types()
• scholidonline_capabilities()
• id_exists()
• id_convert()
• id_metadata()
• id_links()

Supported identifier types

You can inspect which identifier types are supported:

scholidonline::scholidonline_types()
#> [1] "arxiv" "doi"   "orcid" "pmcid" "pmid"

Inspecting capabilities

scholidonline is registry-driven. You can inspect all supported operations, conversions, and providers:

out <- scholidonline::scholidonline_capabilities()
knitr::kable(out)

Existence checks: id_exists()

id_exists() verifies whether identifiers exist in their respective registries.

scholidonline::id_exists(
  x    = "10.1000/182",
  type = "doi"
)

If type = NULL, the type is inferred automatically:

scholidonline::id_exists(
  x = c(
    "10.1000/182",
    "12345678"
  )
)

Return values:

• TRUE → confirmed by registry
• FALSE → confirmed not found
• NA → cannot be classified or normalized

Conversion: id_convert()

Many scholarly identifiers are cross-linked across systems.

Common examples:

• PMID → DOI
• PMCID → PMID
• DOI → PMCID

scholidonline::id_convert(
  x    = "12345678",
  from = "pmid",
  to   = "doi"
)

If from = NULL, the source type is inferred per element:

scholidonline::id_convert(
  x = c("12345678", "PMC1234567"),
  to = "doi"
)

Unresolvable mappings return NA_character_.

Metadata retrieval: id_metadata()

id_metadata() retrieves harmonized metadata from external registries.

out <- scholidonline::id_metadata(
  x    = "10.1038/nature12373",
  type = "doi"
)
knitr::kable(out)

Metadata completeness depends on the registry.

You can restrict returned fields:

out <- scholidonline::id_metadata(
  x = "10.1038/nature12373",
  type = "doi",
  fields = c("title", "year", "doi")
)
knitr::kable(out)

Linked identifiers: id_links()

id_links() returns related identifiers discovered via registry queries.

out <- scholidonline::id_links(
  x    = "PMC1234567",
  type = "pmcid"
)
knitr::kable(out)

The result is a long data.frame with one row per link.

Working with mixed data

A common workflow for messy identifier columns:

1. Detect identifier types (via scholid)
2. Normalize identifiers
3. Check registry existence

Example:

x <- c(
  "https://doi.org/10.1000/182",
  "PMCID: PMC1234567",
  "not an id"
)

types <- scholid::detect_scholid_type(x)

x_norm <- rep(NA_character_, length(x))

for (i in seq_along(x)) {
  if (is.na(types[i])) {
    next
  }

  x_norm[i] <- scholid::normalize_scholid(
    x = x[i],
    type = types[i]
  )
}

types
x_norm

scholidonline::id_exists(x)

Provider selection

Most functions accept a provider argument.

scholidonline::id_exists(
  x        = "10.1000/182",
  type     = "doi",
  provider = "crossref"
)

scholidonline::id_exists(
  x        = "10.1000/182",
  type     = "doi",
  provider = "doi.org"
)

If provider = "auto" (default), a sensible registry is chosen automatically, potentially with fallback behavior.

Available providers depend on the identifier type and operation. Use scholidonline_capabilities() to inspect them.

The chosen provider affects:

• Response speed
• Metadata richness
• Crosswalk coverage

Scope of scholidonline

scholidonline focuses on identifiers that have:

• Stable public registries
• Accessible APIs
• Meaningful cross-system relationships

Examples:

• DOI
• PMID
• PMCID
• ORCID
• arXiv

Other identifiers (e.g., ISBN, ISSN) are structurally supported by scholid, but do not always have stable, open registry APIs.