Title: Toolkit for the 'Entrez' API
Version: 0.1.0
Description: Interact with the 'Entrez' API hosted by the National Center for Biotechnology Information (NCBI), https://www.ncbi.nlm.nih.gov/books/NBK25499/. This package is focused on working with sequence metadata and links. It handles pagination and compensates for some API limitations to simplify these tasks. API calls are printed to the console to highlight how high-level queries are translated into individual HTTP requests.
License: MIT + file LICENSE
Encoding: UTF-8
RoxygenNote: 7.3.3
Collate: 'count.R' 'process.R' 'fetch.R' 'id_set.R' 'id_set_validate.R' 'info.R' 'jentre-package.R' 'link.R' 'post.R' 'request.R' 'search.R' 'utils.R'
Depends: R (≥ 4.1.0)
Imports: cli, glue, httr2, purrr, rlang (≥ 1.1.0), vctrs (≥ 0.7.0), xml2
Suggests: httpuv, testthat (≥ 3.0.0), tibble, withr
Config/testthat/edition: 3
URL: https://github.com/cidm-ph/jentre, https://cidm-ph.github.io/jentre/
BugReports: https://github.com/cidm-ph/jentre/issues
NeedsCompilation: no
Packaged: 2026-03-25 06:10:45 UTC; csus5157
Author: Carl Suster ORCID iD [aut, cre, cph]
Maintainer: Carl Suster <carl.suster@sydney.edu.au>
Repository: CRAN
Date/Publication: 2026-03-30 08:50:13 UTC

jentre: Toolkit for the 'Entrez' API

Description

To use this package effectively, you should have some understanding of the design of the Entrez API which is documented at https://www.ncbi.nlm.nih.gov/books/NBK25500/. Helper functions will make it easier to avoid common pitfalls, and to make use of features like pagination, but you'll still need to understand how to structure your requests efficiently to avoid undue load.

Details

Entrez API usage is subject to guidelines that are available at the URL above. Entrez datasets are also subject to copyright. Refer to the NCBI policies at https://www.ncbi.nlm.nih.gov/home/about/policies/ for details.

Author(s)

Maintainer: Carl Suster carl.suster@sydney.edu.au (ORCID) [copyright holder]

See Also

Useful links:

Check ID set is well formed

Description

Check ID set is well formed

Usage

check_id_set(
  x,
  database = NULL,
  arg = rlang::caller_arg(x),
  call = rlang::caller_env()
)

check_id_list(x, arg = rlang::caller_arg(x), call = rlang::caller_env())

check_web_history(x, arg = rlang::caller_arg(x), call = rlang::caller_env())

entrez_database(x)

Arguments

x

ID set object.

database

name of intended database. If NULL the database name is not checked.

arg

name of argument to use in error reporting.

call

execution environment, for error reporting. See rlang::topic-error-call and the call argument of cli::cli_abort().

Value

Fetch records from Entrez

Description

Fetching can be slow, and Entrez will time out requests that take too long. This helper supports pagination if you specify retmax.

Usage

efetch(
  id_set,
  ...,
  retstart = 0L,
  retmax = NA,
  retmode = "xml",
  rettype = NULL,
  .method = NA,
  .cookies = NA,
  .paginate = 200L,
  .process = NA,
  .progress = "Fetching",
  .path = NULL,
  .call = rlang::current_env()
)

Arguments

id_set

ID set object.

...

additional API parameters (refer to Entrez documentation). Any set to NULL are removed.

retstart

integer: index of first result (starts from 0).

retmax

integer: maximum number of results to return. When NA this returns all results. When NULL, uses the Entrez default (typically 20). Note that when using pagination with web history, it is possible that slightly more than retmax results will be returned.

retmode

character: requested document file format.

rettype

character: requested document type.

.method

HTTP verb. If NA, a sensible default is chosen based on the request parameters.

.cookies

path to persist cookies. If NULL, cookies are not added to the request. For helper functions: when NA, a temporary file is created (in this case only, the temporary file will be cleaned up once all requests are performed).

.paginate

controls how multiple API requests are used to complete the call. Pagination is performed using the retstart and retmax API parameters. When set to an integer, no more than .pagniate items will be requested per API call. When FALSE or 0, only one API request is sent.

.process

function that processes the API results. Can be a function or builtin processor as described in process. Additional builtin processors are available:

  • "uilist" to extract a list of IDs (suitable for rettype = "uilist"),

  • NA to use a sensible choice based on parameters. In particular, for "uilist" requests, it will return an id_list object.

.progress

controls progress bar; see the progress argument of httr2::req_perform_iterative().

.path

path specification for saving raw responses. See path argument of httr2::req_perform_iterative().

.call

call environment to use in error messages/traces. See rlang::topic-error-call and the call argument of cli::cli_abort(). You only need to specify this in internal helper functions that don't need to be mentioned in error messages.

Value

Combined output of .process from each page of results. For the default where .process does nothing, this will be a list of XML documents. For other choices, it can be a vector, list, or data frame.

See Also

Other API methods: einfo(), elink(), entrez_validate(), epost(), esearch(), esummary()

Examples

library(xml2)
id_set <- id_list("sra", c("39889350", "39889348", "39889347"))

## Not run: 
efetch(id_set)
# -> efetch db="sra" retstart="0" retmax="3" retmode="xml" * id="39889350,...,39889347"[3]
# [[1]]
# {xml_document}
# <EXPERIMENT_PACKAGE_SET>
# [1] <EXPERIMENT_PACKAGE>\n  <EXPERIMENT accession="SRX29833825" alias="24-MYP-0283_50325"> ...
# [2] <EXPERIMENT_PACKAGE>\n  <EXPERIMENT accession="SRX29833823" alias="24-MYP-0273_50325"> ...
# [3] <EXPERIMENT_PACKAGE>\n  <EXPERIMENT accession="SRX29833822" alias="24-MYP-0270_50325"> ...

extract_alias <- function(document) {
  xml_find_all(document, "//EXPERIMENT/@alias") |> xml_text()
}
efetch(id_set, .process = extract_alias)
# -> efetch db="sra" retstart="0" retmax="3" retmode="xml" * id="39889350,...,39889347"[3]
# [1] "24-MYP-0283_50325" "24-MYP-0273_50325" "24-MYP-0270_50325"
## End(Not run)

Get details about Entrez databases

Description

These functions call the EInfo endpoint. einfo() provides the number of entries in the databases, the name and description, list of terms usable in the query syntax, and list of link names usable with the ELink endpoint.

Usage

einfo(db, ..., retmode = "xml", version = "2.0", .call = rlang::current_env())

einfo_databases(..., retmode = "xml", .call = rlang::current_env())

Arguments

db

name of database to provide information about.

...

additional API parameters (refer to Entrez documentation). Any set to NULL are removed.

retmode

response format.

version

response format version.

.call

call environment to use in error messages/traces. See rlang::topic-error-call and the call argument of cli::cli_abort(). You only need to specify this in internal helper functions that don't need to be mentioned in error messages.

Value

Character vector of database names for einfo_databases(). An XML document with root node ⁠<eInfoResult>⁠ for einfo().

See Also

Other API methods: efetch(), elink(), entrez_validate(), epost(), esearch(), esummary()

Examples

library(xml2)

## Not run: 
einfo("sra") |> xml_find_first("//Description") |> xml_text()
# [1] "SRA Database"
## End(Not run)

Description

elink() offers direct access to the ELink API endpoint, which has many different input and output formats depending on parameters. If you just want a one-to-one mapping of neighbor links, use elink_map(), which handles this for you.

Usage

elink(
  id_set,
  db,
  ...,
  retmode = "xml",
  cmd = NA,
  .paginate = 100L,
  .process = NA,
  .method = NA,
  .multi = "explode",
  .progress = TRUE,
  .cookies = NA,
  .path = NULL,
  .call = current_env()
)

elink_map(id_set, db, ..., .cookies = NA, .path = NULL, .call = current_env())

Arguments

id_set

ID set object.

db

target database name.

...

additional API parameters (refer to Entrez documentation). Any set to NULL are removed.

retmode

response format.

cmd

ELink command. If NA either "neighbor" or "neighbor_history" will be used based on the type of input.

.paginate

maximum number of UIDs to submit per request. .paginate only applies when id_set is an explicit list. Set to FALSE to prevent batching.

.process

function that processes the API results. Can be a function or builtin processor as described in process. Additional builtin processors are available: "sets" to get a data frame of ID set objects, "flat" to get a data frame of UIDs, or NA to use a sensible choice based on parameters.

.method

HTTP verb. For "POST", any params with vector values (usually just id) are sent in the request body instead of the URL.

.multi

controls how repeated params are handled (see httr2::req_url_query()).

.progress

controls progress bar; see the progress argument of httr2::req_perform_iterative().

.cookies

path to persist cookies. If NULL, cookies are not added to the request. For helper functions: when NA, a temporary file is created (in this case only, the temporary file will be cleaned up once all requests are performed).

.path

path specification for saving raw responses. See path argument of httr2::req_perform_iterative().

.call

call environment to use in error messages/traces. See rlang::topic-error-call and the call argument of cli::cli_abort(). You only need to specify this in internal helper functions that don't need to be mentioned in error messages.

Value

concatenated output of .process. For elink(.process = "sets") a data frame with columns

from

Source link set.

to

Target link set.

linkname

Link name (see https://eutils.ncbi.nlm.nih.gov/entrez/query/static/entrezlinks.html or einfo).

For elink_map() and elink(.process = "flat") a data frame with columns

db_from

Source database name.

id_from

Source identifier. Can be a list column depending on how elink was called.

db_to

Target database name.

linkname

Link name (see https://eutils.ncbi.nlm.nih.gov/entrez/query/static/entrezlinks.html or einfo).

id_to

Target identifier. In general this will be a list column.

One-to-one mapping

Note that some ways of calling this API on multiple UIDs result in the one-to-one association of the input and output sets getting lost. The way around this is to specify each ID as a separate parameter rather than a single comma-separated param. This is handled by the default choice of .multi = "explode". When using a web history token as input, there is no corresponding way to ensure one-to-one mapping. To ensure that the result is always one-to-one, use elink_map(), which may make several API requests to achieve the result.

See Also

Other API methods: efetch(), einfo(), entrez_validate(), epost(), esearch(), esummary()

Examples

id_set <- id_list("sra", c("39889350", "39889348", "39889347"))

## Not run: 
links <- elink(id_set, "bioproject", linkname = "sra_bioproject")
# -> elink db="bioproject" dbfrom="sra" retmode="xml" cmd="neighbor" linkname="sra_bioproject"
#    * id="39889350" id="39889348" id="39889347"
links
# # A tibble: 3 x 5
#   db_from id_from   db_to      linkname       id_to
#   <chr>   <list>    <chr>      <chr>          <list>
# 1 sra     <chr [1]> bioproject sra_bioproject <chr [1]>
# 2 sra     <chr [1]> bioproject sra_bioproject <chr [1]>
# 3 sra     <chr [1]> bioproject sra_bioproject <chr [1]>

links[c("id_from", "id_to")] |> igraph::graph_from_data_frame()
# IGRAPH a807b82 DN-- 4 3 --
# + attr: name (v/c)
# + edges from a807b82 (vertex names):
# [1] 39889350->1241475 39889348->1241475 39889347->1241475
## End(Not run)

Count the number of entries in an ID set

Description

If id_set is an id_list then this is equivalent to length(). If it is a web_history, this may involve an Entrez API call to get the number of entries. In this case the result is cached so that subsequent calls don't hit the API again.

Usage

entrez_count(id_set, .call = current_env())

Arguments

id_set

an ID set object.

.call

call environment to use in error messages/traces. See rlang::topic-error-call and the call argument of cli::cli_abort(). You only need to specify this in internal helper functions that don't need to be mentioned in error messages.

Value

integer number of entries.

Examples

id_set <- id_list("sra", c("39889350", "39889348", "39889347"))
entrez_count(id_set)

Construct a request to the Entrez API

Description

This is a low-level helper that builds a request object but does not perform the request. In general you'll likely use higher-level methods like efetch() instead.

Usage

entrez_request(
  endpoint,
  ...,
  .method = "GET",
  .multi = "comma",
  .cookies = NULL,
  .verbose = getOption("jentre.verbose", default = TRUE),
  .call = current_env()
)

entrez_api_key(default = NULL)

Arguments

endpoint

Entrez endpoint name (e.g. "efetch.fcgi").

...

additional API parameters (refer to Entrez documentation). Any set to NULL are removed.

.method

HTTP verb. For "POST", any params with vector values (usually just id) are sent in the request body instead of the URL.

.multi

controls how repeated params are handled (see httr2::req_url_query()).

.cookies

path to persist cookies. If NULL, cookies are not added to the request. For helper functions: when NA, a temporary file is created (in this case only, the temporary file will be cleaned up once all requests are performed).

.verbose

logical: when TRUE logs all API requests as messages in a compact format. This uses a summarised format that does not include the request body for POST. Use normal httr verbosity controls (e.g. httr2::local_verbosity()) to override this behaviour and see more details.

.call

call environment to use in error messages/traces. See rlang::topic-error-call and the call argument of cli::cli_abort(). You only need to specify this in internal helper functions that don't need to be mentioned in error messages.

default

default value to return if no global configuration is found.

Details

email, tool, and api_key have default values but these can be overridden, or can be removed by setting them to NULL.

Value

API limits

The Entrez APIs are rate limited. Requests in this package respect the API headers returned by Entrez. Without an API key you will be rate limited more aggressively, so it is recommended to obtain an API key. jentre searches for the API key in the following order:

You can check the value is found properly using entrez_api_key(). If no API key is set, a warning will be displayed. This can be suppressed by setting the option "jentre.silence_api_warning" to TRUE.

Examples

library(httr2)

req <- entrez_request("esearch.fcgi", db = "nucleotide", term = "biomol+trna[prop]")
## Not run: 
# You'll need to perform the request with httr2 and parse it yourself:
req_perform(req) |> resp_body_xml()
## End(Not run)

Look up accessions and other IDs on Entrez

Description

Passes the provided IDs through Entrez which has the effect of normalising the accepted UIDs, and removing invalid UIDs. For web history lists, this forces results to be freshly downloaded (unlike as_id_list() which can use cached results).

Usage

entrez_validate(id_set, .paginate = 5000L, .path = NULL, .call = current_env())

Arguments

id_set

an id_list object.

.paginate

controls how multiple API requests are used to complete the call. Pagination is performed using the retstart and retmax API parameters. When set to an integer, no more than .pagniate items will be requested per API call. When FALSE or 0, only one API request is sent.

.path

path specification for saving raw responses.

.call

call environment to use in error messages/traces. See rlang::topic-error-call and the call argument of cli::cli_abort(). You only need to specify this in internal helper functions that don't need to be mentioned in error messages.

Value

id_list object

See Also

Other API methods: efetch(), einfo(), elink(), epost(), esearch(), esummary()

Examples

id_set <- id_list("sra", c("SRX29833825", "SRX29833823", "SRX29833822"))
## Not run: 
entrez_validate(id_set)
# <entrez/sra[3]>
# [1] 39889350 39889348 39889347
## End(Not run)

Register UIDs with the Entrez history server

Description

Register UIDs with the Entrez history server

Usage

epost(id_set, ..., WebEnv = NULL, .path = NULL, .call = rlang::current_env())

Arguments

id_set

an id_list object.

...

additional API parameters (refer to Entrez documentation). Any set to NULL are removed.

WebEnv

either a character to pass on as-is, or a web_history object.

.path

path specification for saving raw responses.

.call

call environment to use in error messages/traces. See rlang::topic-error-call and the call argument of cli::cli_abort(). You only need to specify this in internal helper functions that don't need to be mentioned in error messages.

Value

A web_history object usable with other API functions.

See Also

Other API methods: efetch(), einfo(), elink(), entrez_validate(), esearch(), esummary()

Examples

id_set <- id_list("sra", c("39889350", "39889348", "39889347"))

## Not run: 
epost(id_set)
# -> epost db="sra" * id="39889350,...,39889347"[3]
# <entrez@/sra[1]>
# [1] MCID_69c36.#1[3]
## End(Not run)

Search Entrez databases

Description

The search term field names are documented in the EInfo API endpoint: see einfo().

Usage

esearch(
  term,
  db,
  ...,
  retstart = 0L,
  retmax = NA,
  retmode = "xml",
  rettype = "uilist",
  usehistory = is.null(retmax) || is.na(retmax),
  WebEnv = NULL,
  query_key = NULL,
  .cookies = NA,
  .paginate = 10000L,
  .progress = "ESearch",
  .path = NULL,
  .verbose = getOption("jentre.verbose", default = TRUE),
  .call = current_env()
)

Arguments

term

search query.

db

Entrez database name.

...

additional API parameters (refer to Entrez documentation). Any set to NULL are removed.

retstart

integer: index of first result (starts from 0). Ignored when usehistory is TRUE.

retmax

integer: maximum number of results to return. When NA this returns all results. When NULL, uses the Entrez default (typically 20). Note that it is possible that slightly more than retmax results will be returned when paginating. Ignored when usehistory is TRUE.

retmode

character: currently only "xml" is supported.

rettype

character: currently only "uilist" is supported.

usehistory

logical: when TRUE use the history server to return the result.

WebEnv, query_key

either characters to pass on as-is, or web_history objects.

.cookies

path to persist cookies. If NULL, cookies are not added to the request. For helper functions: when NA, a temporary file is created (in this case only, the temporary file will be cleaned up once all requests are performed).

.paginate

controls how multiple API requests are used to complete the call. Pagination is performed using the retstart and retmax API parameters. When set to an integer, no more than .pagniate items will be requested per API call. When FALSE or 0, only one API request is sent. Ignored when usehistory is TRUE.

.progress

controls progress bar; see the progress argument of httr2::req_perform_iterative().

.path

path specification for saving raw responses. See path argument of httr2::req_perform_iterative().

.verbose

logical: when TRUE logs all API requests as messages in a compact format. This uses a summarised format that does not include the request body for POST. Use normal httr verbosity controls (e.g. httr2::local_verbosity()) to override this behaviour and see more details.

.call

call environment to use in error messages/traces. See rlang::topic-error-call and the call argument of cli::cli_abort(). You only need to specify this in internal helper functions that don't need to be mentioned in error messages.

Value

An id set object (either a web_history or an id_list).

See Also

https://www.ncbi.nlm.nih.gov/books/NBK25499/#chapter4.ESearch

Other API methods: efetch(), einfo(), elink(), entrez_validate(), epost(), esummary()

Examples

## Not run: 
esearch("mpox virus[orgn]", "biosample")
# -> esearch db="biosample" term="mpox virus[orgn]" retmode="xml" rettype="uilist" usehistory="y"
#  i eSearch query "\"Monkeypox virus\"[Organism]" has 7189 results
# <entrez@/biosample[1]>
# [1] MCID_69c36.#1[7189]

## End(Not run)

Fetch document summaries from Entrez

Description

ESummary is faster than EFetch because it only interacts with the frontend rather than the full database. It contains more limited information.

Usage

esummary(
  id_set,
  ...,
  retstart = 0L,
  retmax = NA,
  retmode = "xml",
  version = "2.0",
  .method = NA,
  .cookies = NA,
  .paginate = 5000L,
  .process = "identity",
  .progress = "Fetching summaries",
  .path = NULL,
  .call = rlang::current_env()
)

Arguments

id_set

ID set object.

...

additional API parameters (refer to Entrez documentation). Any set to NULL are removed.

retstart

integer: index of first result (starts from 0).

retmax

integer: maximum number of results to return. When NA this returns all results. When NULL, uses the Entrez default (typically 20). Note that when using pagination with web history, it is possible that slightly more than retmax results will be returned.

retmode

character: requested document file format.

version

character: requested format version.

.method

HTTP verb. If NA, a sensible default is chosen based on the request parameters.

.cookies

path to persist cookies. If NULL, cookies are not added to the request. For helper functions: when NA, a temporary file is created (in this case only, the temporary file will be cleaned up once all requests are performed).

.paginate

controls how multiple API requests are used to complete the call. Pagination is performed using the retstart and retmax API parameters. When set to an integer, no more than .pagniate items will be requested per API call. When FALSE or 0, only one API request is sent.

.process

function that processes the API results. Can be a function or builtin processor as described in process. Additional builtin processors are available:

  • "uilist" to extract a list of IDs (suitable for rettype = "uilist"),

  • NA to use a sensible choice based on parameters. In particular, for "uilist" requests, it will return an id_list object.

.progress

controls progress bar; see the progress argument of httr2::req_perform_iterative().

.path

path specification for saving raw responses. See path argument of httr2::req_perform_iterative().

.call

call environment to use in error messages/traces. See rlang::topic-error-call and the call argument of cli::cli_abort(). You only need to specify this in internal helper functions that don't need to be mentioned in error messages.

Value

Combined output of .process from each page of results. For the default where .process does nothing, this will be a list of XML documents. For other choices, it can be a vector, list, or data frame.

See Also

Other API methods: efetch(), einfo(), elink(), entrez_validate(), epost(), esearch()

Entrez identifier sets

Description

Many Entrez APIs accept either a UID list or tokens that point to a result stored on its history server. The classes here wrap these and keep track of the database name that the identifiers belong to. Most of the API helpers in this package are generic over the type of ID set and so can be used the same way with either type.

Usage

id_list(db, ids = character())

web_history(db, WebEnv, query_key, length = NA)

is_id_set(x)

is_id_list(x)

is_web_history(x)

as_id_list(x, .paginate = 5000L, .path = NULL, .call = current_env())

Arguments

db

name of the associated Entrez database (e.g. "biosample").

ids

UIDs, coercible to a character vector (can be accessions or GI numbers).

query_key, WebEnv

history server tokens returned by another Entrez API call.

length

number of UIDs in the set, if known.

x

object to test or convert.

.paginate

controls how multiple API requests are used to complete the call. Pagination is performed using the retstart and retmax API parameters. When set to an integer, no more than .pagniate items will be requested per API call. When FALSE or 0, only one API request is sent. Ignored when usehistory is TRUE.

.path

path specification for saving raw responses. See path argument of httr2::req_perform_iterative().

.call

call environment to use in error messages/traces. See rlang::topic-error-call and the call argument of cli::cli_abort(). You only need to specify this in internal helper functions that don't need to be mentioned in error messages.

Details

It usually will not make sense to create web_history() objects directly - they are short-lived pointers to results on the Entrez history server and are created by other API calls.

id_list is a vector and can be manipulated to take subsets (e.g. id_set[1:10] or tail(id_set)).

web_history is an opaque reference to an ID list stored on the Entrez history server. Through the course of API calls, information about the length or the actual list of IDs may be discovered and cached, avoiding subsequent API calls. as_id_list() can be used to extract the list of IDs.

Convert id_list to web_history with epost(). Convert web_history to id_list with as_id_list().

Value

See Also

entrez_validate() and entrez_count()

Examples

bioprojects <- id_list("bioproject", c("1241475"))

Process API results

Description

Function to turn the parsed response document into meaningful data. It must accept one argument, doc, the parsed response document. The return value must be compatible with vctrs::list_combine(), e.g. a vector, list, or data frame.

Details

API results are parsed based on the retmode parameter. XML documents will be parsed into xml2::xml_document objects and an error will be raised if it contains an ⁠<ERROR>⁠ node.

Builtin processors can be referred to by name instead of specifying your own function. Some helpers provide additional processors, but these are always available: