select {ensembldb} | R Documentation

## Integration into the AnnotationDbi framework

### Description

Several of the methods available for `AnnotationDbi` objects are also implemented for `EnsDb` objects. This enables to extract data from `EnsDb` objects in a similar fashion than from objects inheriting from the base annotation package class `AnnotationDbi`. In addition to the standard usage, the `select` and `mapIds` for `EnsDb` objects support also the filter framework of the ensembdb package and thus allow to perform more fine-grained queries to retrieve data.

### Usage

    ## S4 method for signature 'EnsDb'
    columns(x)
    ## S4 method for signature 'EnsDb'
    keys(x, keytype, filter,...)
    ## S4 method for signature 'EnsDb'
    keytypes(x)
    ## S4 method for signature 'EnsDb'
    mapIds(x, keys, column, keytype, ..., multiVals)
    ## S4 method for signature 'EnsDb'
    select(x, keys, columns, keytype, ...)

### Arguments

(In alphabetic order)

`column` | For `mapIds`: the column to search on, i.e. from which values should be retrieved.
`columns` | For `select`: the columns from which values should be retrieved. Use the `columns` method to list all possible columns.
`keys` | The keys/ids for which data should be retrieved from the database. This can be either a character vector of keys/IDs, a single filter object extending `AnnotationFilter`, an combination of filters `AnnotationFilterList` or a `formula` representing a filter expression (see `AnnotationFilter` for more details).
`keytype` | For `mapIds` and `select`: the type (column) that matches the provided keys. This argument does not have to be specified if argument `keys` is a filter object extending `AnnotationFilter` or a `list` of such objects. For `keys`: which keys should be returned from the database.
`filter` | For `keys`: either a single object extending `AnnotationFilter` or a list of such object to retrieve only specific keys from the database.
`multiVals` | What should `mapIds` do when there are multiple values that could be returned? Options are: `"first"` (default), `"list"`, `"filter"`, `"asNA"`. See `mapIds` in the `AnnotationDbi` package for a detailed description.
`x` | The `EnsDb` object.
`...` | Not used.

### Value

See method description above.

### Methods and Functions

columns

  List all the columns that can be retrieved by the `mapIds` and `select` methods. Note that these column names are different from the ones supported by the `genes`, `transcripts` etc. methods that can be listed by the `listColumns` method.

  Returns a character vector of supported column names.

keys

  Retrieves all keys from the column name specified with `keytype`. By default (if `keytype` is not provided) it returns all gene IDs. Note that `keytype="TXNAME"` will return transcript ids, since no transcript names are available in the database.

  Returns a character vector of IDs.

keytypes

  List all supported key types (column names).

  Returns a character vector of key types.

mapIds

  Retrieve the mapped ids for a set of keys that are of a particular keytype. Argument `keys` can be either a character vector of keys/IDs, a single filter object extending `AnnotationFilter` or a list of such objects. For the latter, the argument `keytype` does not have to be specified. Importantly however, if the filtering system is used, the ordering of the results might not represent the ordering of the keys.

  The method usually returns a named character vector or, depending on the argument `multiVals` a named list, with names corresponding to the keys (same ordering is only guaranteed if `keys` is a character vector).

select

  Retrieve the data as a `data.frame` based on parameters for selected `keys`, `columns` and `keytype` arguments. Multiple matches of the keys are returned in one row for each possible match. Argument `keys` can be either a character vector of keys/IDs, a single filter object extending `AnnotationFilter` or a list of such objects. For the latter, the argument `keytype` does not have to be specified.

  Note that values from a column `"TXNAME"` will be the same than for a column `"TXID"`, since internally no database column `"tx_name"` is present and the column is thus mapped to `"tx_id"`.

  Returns a `data.frame` with the column names corresponding to the argument `columns` and rows with all data matching the criteria specified with `keys`.

  The use of `select` without filters or keys and without restricting to specicic columns is strongly discouraged, as the SQL query to join all of the tables, especially if protein annotation data is available is very expensive.

### Author(s)

Johannes Rainer

### See Also

`listColumns` `transcripts`

### Examples

    library(EnsDb.Hsapiens.v86)
    edb <- EnsDb.Hsapiens.v86

    ## List all supported keytypes.
    keytypes(edb)

    ## List all supported columns for the select and mapIds methods.
    columns(edb)

    ## List /real/ database column names.
    listColumns(edb)

    ## Retrieve all keys corresponding to transcript ids.
    txids <- keys(edb, keytype = "TXID")
    length(txids)
    head(txids)

    ## Retrieve all keys corresponding to gene names of genes encoded on chromosome X
    gids <- keys(edb, keytype = "GENENAME", filter = SeqNameFilter("X"))
    length(gids)
    head(gids)

    ## Get a mapping of the genes BCL2 and BCL2L11 to all of their
    ## transcript ids and return the result as list
    maps <- mapIds(edb, keys = c("BCL2", "BCL2L11"), column = "TXID",
                   keytype = "GENENAME", multiVals = "list")
    maps

    ## Perform the same query using a combination of a GeneNameFilter and a
    ## TxBiotypeFilter to just retrieve protein coding transcripts for these
    ## two genes.
    mapIds(edb, keys = list(GeneNameFilter(c("BCL2", "BCL2L11")),
                            TxBiotypeFilter("protein_coding")), column = "TXID",
           multiVals = "list")

    ## select:
    ## Retrieve all transcript and gene related information for the above example.
    select(edb, keys = list(GeneNameFilter(c("BCL2", "BCL2L11")),
                            TxBiotypeFilter("protein_coding")),
           columns = c("GENEID", "GENENAME", "TXID", "TXBIOTYPE", "TXSEQSTART",
                       "TXSEQEND", "SEQNAME", "SEQSTRAND"))

    ## Get all data for genes encoded on chromosome Y
    Y <- select(edb, keys = "Y", keytype = "SEQNAME")
    head(Y)
    nrow(Y)

    ## Get selected columns for all lincRNAs encoded on chromosome Y. Here we use
    ## a filter expression to define what data to retrieve.
    Y <- select(edb, keys = ~ seq_name == "Y" & gene_biotype == "lincRNA",
                columns = c("GENEID", "GENEBIOTYPE", "TXID", "GENENAME"))
    head(Y)
    nrow(Y)

[Package ensembldb version 2.18.4 Index]