clusterCTSS {CAGEr} | R Documentation

## Cluster CTSSs into tag clusters

### Description

Clusters individual CAGE transcription start sites (CTSSs) along the genome into tag clusters (TCs) using specified ab initio method, or assigns them to predefined genomic regions.

### Usage

    clusterCTSS(object, threshold = 1, nrPassThreshold = 1,
      thresholdIsTpm = TRUE, method = c("distclu", "paraclu", "custom"),
      maxDist = 20, removeSingletons = FALSE, keepSingletonsAbove = Inf,
      minStability = 1, maxLength = 500, reduceToNonoverlapping = TRUE,
      customClusters = NULL, useMulticore = FALSE, nrCores = NULL)

    ## S4 method for signature 'CAGEset'
    clusterCTSS(object, threshold = 1,
      nrPassThreshold = 1, thresholdIsTpm = TRUE, method = c("distclu",
      "paraclu", "custom"), maxDist = 20, removeSingletons = FALSE,
      keepSingletonsAbove = Inf, minStability = 1, maxLength = 500,
      reduceToNonoverlapping = TRUE, customClusters = NULL,
      useMulticore = FALSE, nrCores = NULL)

    ## S4 method for signature 'CAGEexp'
    clusterCTSS(object, threshold = 1,
      nrPassThreshold = 1, thresholdIsTpm = TRUE, method = c("distclu",
      "paraclu", "custom"), maxDist = 20, removeSingletons = FALSE,
      keepSingletonsAbove = Inf, minStability = 1, maxLength = 500,
      reduceToNonoverlapping = TRUE, customClusters = NULL,
      useMulticore = FALSE, nrCores = NULL)

### Arguments

`object` | A `CAGEr` object.
`threshold, nrPassThreshold` | Ignore CTSSs with signal `< threshold` in `< nrPassThreshold` experiments.
`thresholdIsTpm` | Logical indicating if `threshold` is expressed in raw tag counts (`FALSE`) or normalized signal (`TRUE`).
`method` | Method to be used for clustering: `"distclu"`, `"paraclu"` or `"custom"`. See Details.
`maxDist` | Maximal distance between two neighbouring CTSSs for them to be part of the same cluster. Used only when `method = "distclu"`, otherwise ignored.
`removeSingletons` | Logical indicating if tag clusters containing only one CTSS be removed. Ignored when `method = "custom"`.
`keepSingletonsAbove` | Controls which singleton tag clusters will be removed. When `removeSingletons = TRUE`, only singletons with signal `< keepSingletonsAbove` will be removed. Useful to prevent removing highly supported singleton tag clusters. Default value `Inf` results in removing all singleton TCs when `removeSingletons = TRUE`. Ignored when `method = "custom"`.
`minStability` | Minimal stability of the cluster, where stability is defined as ratio between maximal and minimal density value for which this cluster is maximal scoring. For definition of stability refer to Frith et al., Genome Research, 2007. Clusters with stability `< minStability` will be discarded. Used only when `method = "paraclu"`.
`maxLength` | Maximal length of cluster in base-pairs. Clusters with length `> maxLength` will be discarded. Ignored when `method = "custom"`.
`reduceToNonoverlapping` | Logical, should smaller clusters contained within bigger cluster be removed to make a final set of tag clusters non-overlapping. Used only `method = "paraclu"`.
`customClusters` | Genomic coordinates of predefined regions to be used to segment the CTSSs. The format is either a `GRanges` object or a `data.frame` with the following columns: `chr` (chromosome name), `start` (0-based start coordinate), `end` (end coordinate), `strand` (either `"+"`, or `"-"`). Used only when `method = "custom"`.
`useMulticore` | Logical, should multicore be used. `useMulticore = TRUE` has no effect on non-Unix-like platforms.
`nrCores` | Number of cores to use when `useMulticore = TRUE`. Default value `NULL` uses all detected cores.

### Details

The `"distclu"` method is an implementation of simple distance-based clustering of data attached to sequences, where two neighbouring TSSs are joined together if they are closer than some specified distance (see `distclu-functions` for implementation details.

`"paraclu"` is an implementation of Paraclu algorithm for parametric clustering of data attached to sequences (Frith et al., Genome Research, 2007). Since Paraclu finds clusters within clusters (unlike distclu), additional parameters (`removeSingletons`, `keepSingletonsAbove`, `minStability`, `maxLength` and `reduceToNonoverlapping`) can be specified to simplify the output by discarding too small (singletons) or too big clusters, and to reduce the clusters to a final set of non-overlapping clusters.

Clustering is done for every CAGE dataset within the CAGEr object separately, resulting in a different set of tag clusters for every CAGE dataset. TCs from different datasets can further be aggregated into a single referent set of consensus clusters by calling the `aggregateTagClusters` function.

### Value

The slots `clusteringMethod`, `filteredCTSSidx` and `tagClusters` of the provided `CAGEset` object will be occupied by the information on method used for clustering, CTSSs included in the clusters and list of tag clusters per CAGE experiment, respectively. To retrieve tag clusters for individual CAGE dataset use the `tagClusters()` function.

In `CAGEexp` objects, the results will be stored as a `GRangesList` of `TagClusters` objects in the metadata slot `tagClusters`. The `TagClusters` objects will contain a `filteredCTSSidx` column if appropriate. The clustering method name is saved in the metadata slot of the `GRangesList`.

### Author(s)

Vanja Haberle

### References

Frith et al. (2007) A code for transcription initiation in mammalian genomes, Genome Research 18(1):1-12, (http://www.cbrc.jp/paraclu/).

### See Also

`tagClusters`, `aggregateTagClusters` and `CTSSclusteringMethod`.

Other CAGEr object modifiers: `CTSStoGenes`, `CustomConsensusClusters`, `aggregateTagClusters`, `annotateCTSS`, `cumulativeCTSSdistribution`, `getCTSS`, `normalizeTagCount`, `quantilePositions`, `summariseChrExpr`

Other CAGEr clusters functions: `CTSSclusteringMethod`, `CTSScumulativesTagClusters`, `CustomConsensusClusters`, `aggregateTagClusters`, `consensusClustersDESeq2`, `consensusClustersGR`, `cumulativeCTSSdistribution`, `plotInterquantileWidth`, `quantilePositions`, `tagClusters`

### Examples

    head(tagClusters(exampleCAGEset, "sample1"))
    clusterCTSS( object = exampleCAGEset, threshold = 50, thresholdIsTpm = TRUE
               , nrPassThreshold = 1, method = "distclu", maxDist = 20
               , removeSingletons = TRUE, keepSingletonsAbove = 100)
    head(tagClusters(exampleCAGEset, "sample1"))

    clusterCTSS( exampleCAGEexp, threshold = 50, thresholdIsTpm = TRUE
               , nrPassThreshold = 1, method = "distclu", maxDist = 20
               , removeSingletons = TRUE, keepSingletonsAbove = 100)
    tagClustersGR(exampleCAGEexp, "Zf.30p.dome")

[Package CAGEr version 1.34.0 Index]