AnnotationHub-objects {AnnotationHub} | R Documentation

## AnnotationHub objects and their related methods and functions

### Description

Use `AnnotationHub` to interact with Bioconductor's AnnotationHub service. Query the instance to discover and use resources that are of interest, and then easily download and import the resource into R for immediate use.

Use `AnnotationHub()` to retrieve information about all records in the hub. If working offline, add argument `localHub=TRUE` to work with a local, non-updated hub; It will only have resources available that have previously been downloaded.

Discover records in a hub using `mcols()`, `query()`, `subset()`, `[`, and `display()`.

Retrieve individual records using `[[`. On first use of a resource, the corresponding files or other hub resources are downloaded from the internet to a local cache. On this and all subsequent uses the files are quickly input from the cache into the R session.

`AnnotationHub` records can be added (and sometimes removed) at any time. `snapshotDate()` restricts hub records to those available at the time of the snapshot. `possibleDates()` lists snapshot dates valid for the current version of Bioconductor.

The location of the local cache can be found (and updated) with `getAnnotationHubCache` and `setAnnotationHubCache`; `removeCache` removes all cache resources.

### Constructors

  `AnnotationHub(..., hub=getAnnotationHubOption("URL"), cache=getAnnotationHubOption("CACHE"), proxy=getAnnotationHubOption("PROXY"), localHub=FALSE)`:

  Create an `AnnotationHub` instance, possibly updating the current database of records.

### Accessors

In the code snippets below, `x` and `object` are AnnotationHub objects.

  `hubCache(x)`: Gets the file system location of the local AnnotationHub cache.

  `hubUrl(x)`: Gets the URL for the online hub.

  `length(x)`: Get the number of hub records.

  `names(x)`: Get the names (AnnotationHub unique identifiers, of the form AH12345) of the hub records.

  `fileName(x)`: Get the file path of the hub records as stored in the local cache (AnnotationHub files are stored as unique numbers, of the form 12345). NA is returned for those records which have not been cached.

  `mcols(x)`: Get the metadata columns describing each record. Columns include:

  title

    Record title, frequently the file name of the object.

  dataprovider

    Original provider of the resource, e.g., Ensembl, UCSC.

  species

    The species for which the record is most relevant, e.g., ‘Homo sapiens’.

  taxonomyid

    NCBI taxonomy identifier of the species.

  genome

    Genome build relevant to the record, e.g., hg19.

  description

    Textual description of the resource, frequently automatically generated from file path and other information available when the record was created.

  tags

    Single words added to the record to facilitate identification, e.g,. TCGA, Roadmap.

  rdataclass

    The class of the R object used to represent the object when imported into R, e.g., `GRanges`, `VCFFile`.

  sourceurl

    Original URL of the resource.

  sourectype

    Format of the original resource, e.g., BED file.

  `dbconn(x)`: Return an open connection to the underyling SQLite database.

  `dbfile(x)`: Return the full path the underyling SQLite database.

  `.db_close(conn)`: Close the SQLite connection `conn` returned by `dbconn(x)`.

### Subsetting and related operations

In the code snippets below, `x` is an AnnotationHub object.

  `x$name`: Convenient reference to individual metadata columns, e.g., `x$species`.

  `x[i]`: Numerical, logical, or character vector (of AnnotationHub names) to subset the hub, e.g., `x[x$species == "Homo sapiens"]`.

  `x[[i]]`: Numerical or character scalar to retrieve (if necessary) and import the resource into R.

  `query(x, pattern, ignore.case=TRUE, pattern.op= `&`)`: Return an AnnotationHub subset containing only those elements whose metadata matches `pattern`. Matching uses `pattern` as in `grepl` to search the `as.character` representation of each column, performing a logical ``&`` across columns. e.g., `query(x, c("Homo sapiens", "hg19", "GTF"))`.

  `pattern`

    A character vector of patterns to search (via `grepl`) for in any of the `mcols()` columns.

  `ignore.case`

    A logical(1) vector indicating whether the search should ignore case (TRUE) or not (FALSE).

  `pattern.op`

    Any function of two arguments, describing how matches across pattern elements are to be combined. The default ``&`` requires that only records with all elements of `pattern` in their metadata columns are returned. ``&``, ``|`` and ``!`` are most notably available. See `"?&"` or `?base::Ops` for more information.

  `subset(x, subset)`: Return the subset of records containing only those elements whose metadata satisfies the expression in `subset`. The expression can reference columns of `mcols(x)`, and should return a logical vector of length `length(x)`. e.g., `subset(x, species == "Homo sapiens" & genome=="GRCh38")`.

  `display(object)`: Open a web browser allowing for easy selection of hub records via interactive tabular display. Return value is the subset of hub records identified while navigating the display.

  `recordStatus(hub, record)`: Returns a `data.frame` of the record id and status. `hub` must be a `Hub` object and `record` must be a `character(1)`. Can be used to discover why a resource was removed from the hub.

### Cache and hub management

In the code snippets below, `x` is an AnnotationHub object.

  `snapshotDate(x)` and `snapshotDate(x) <- value`: Gets or sets the date for the snapshot in use. `value` should be one of `possibleDates()`.

  `possibleDates(x)`: Lists the valid snapshot dates for the version of Bioconductor that is being run (e.g., BiocInstaller::biocVersion()).

  `cache(x)` and `cache(x) <- NULL`: Adds (downloads) all resources in `x`, or removes all local resources corresponding to the records in `x` from the cache. In this case, `x` would typically be a small subset of AnnotationHub resources.

  `hubUrl(x)`: Gets the URL for the online AnnotationHub.

  `hubCache(x)`: Gets the file system location of the local AnnotationHub cache.

  `removeCache(x)`: Removes local AnnotationHub database and all related resources. After calling this function, the user will have to download any AnnotationHub resources again.

### Coercion

In the code snippets below, `x` is an AnnotationHub object.

  `as.list(x)`: Coerce x to a list of hub instances, one entry per element. Primarily for internal use.

  `c(x, ...)`: Concatenate one or more sub-hub. Sub-hubs must reference the same AnnotationHub instance. Duplicate entries are removed.

### Author(s)

Martin Morgan, Marc Carlson, Sonali Arora, and Dan Tenenbaum

### Examples

      ## create an AnnotationHub object
      library(AnnotationHub)
      ah = AnnotationHub()

      ## Summary of available records
      ah

      ## Detail for a single record
      ah[1]

      ## and what is the date we are using?
      snapshotDate(ah)

      ## how many resources?
      length(ah)

      ## from which resources, is data available?
      head(sort(table(ah$dataprovider), decreasing=TRUE))

      ## from which species, is data available ?
      head(sort(table(ah$species),decreasing=TRUE))

      ## what web service and local cache does this AnnotationHub point to?
      hubUrl(ah)
      hubCache(ah)

      ### Examples ###

      ## One can  search the hub for multiple strings
      ahs2 <- query(ah, c("GTF", "77","Ensembl", "Homo sapiens"))

      ## information about the file can be retrieved using
      ahs2[1]

      ## one can further extract information from this show method
      ## like the sourceurl using:
      ahs2$sourceurl
      ahs2$description
      ahs2$title

      ## We can download a file by name like this (using a list semantic):
      gr <- ahs2[[1]]
      ## And we can also extract it by the names like this:
      res <- ah[["AH28812"]]

      ## the gtf file is returned as a GenomicRanges object and contains
      ## data about which organism it belongs to, its seqlevels and seqlengths
      seqinfo(gr)

      ## each GenomicRanges contains a metadata slot which can be used to get
      ## the name of the hub object and other associated metadata.
      metadata(gr)
      ah[metadata(gr)$AnnotationHubName]

      ## And we can also use "[" to restrict the things that are in the
      ## AnnotationHub object (by position, character, or logical vector).
      ## Here is a demo of position:
      subHub <- ah[1:3]

      if(interactive()) {
        ## Display method involves user interaction through web interface
        ah2 <- display(ah)
      }

      ## recordStatus
      recordStatus(ah, "TEST")
      recordStatus(ah, "AH7220")

[Package AnnotationHub version 2.12.1 Index]