extractCytosinesFromFASTA {methimpute} | R Documentation

## Extract cytosine coordinates

### Description

Extract cytosine coordinates and context information from a FASTA file. Cytosines in ambiguous reference contexts are not reported.

### Usage

    extractCytosinesFromFASTA(file, contexts = c("CG", "CHG", "CHH"),
      anchor.C = NULL)

### Arguments

`file` | A character with the file name.
`contexts` | The contexts that should be extracted. If the contexts are named, the returned object will use those names for the contexts.
`anchor.C` | A named vector with positions of the anchoring C in the `contexts`. This is necessary to distinguish contexts such as C*C*CG (anchor.C = 2) and *C*CCG (anchor.C = 1). Names must match the contexts. If unspecified, the first C within each context will be taken as anchor.

### Value

A `GRanges-class` object with coordinates of extracted cytosines and meta-data column 'context'.

### Examples

    ## Read a non-compressed FASTA files:
    filepath <- system.file("extdata", "arabidopsis_sequence.fa.gz", package="methimpute")

    ## Only CG context
    cytosines <- extractCytosinesFromFASTA(filepath, contexts = 'CG')
    table(cytosines$context)

    ## Split CG context into subcontexts
    cytosines <- extractCytosinesFromFASTA(filepath,
                   contexts = c('DCG', 'CCG'),
                   anchor.C = c(DCG=2, CCG=2))
    table(cytosines$context)

    ## With contexts that differ only by anchor
    cytosines <- extractCytosinesFromFASTA(filepath,
                   contexts = c('DCG', 'CCG', 'CCG', 'CWG', 'CHH'),
                   anchor.C = c(DCG=2, CCG=2, CCG=1, CWG=1, CHH=1))
    table(cytosines$context)

    ## With named contexts
    contexts <- c(CG='DCG', CG='CCG', CHG='CCG', CHG='CWG', CHH='CHH')
    cytosines <- extractCytosinesFromFASTA(filepath,
                   contexts = contexts,
                   anchor.C = c(DCG=2, CCG=2, CCG=1, CWG=1, CHH=1))
    table(cytosines$context)

[Package methimpute version 1.6.0 Index]