variantGR2Vcf {VariantTools} | R Documentation

## Create a VCF for some variants

### Description

The deprecated way to create a `VCF` object from a variant/tally `GRanges`. This can then be output to a file using `writeVcf`. The flavor of VCF is specific for calling variants, not genotypes; see below.

### Usage

    variantGR2Vcf(x, sample.id, project = NULL,
                  genome = unique(GenomicRanges::genome(x)))

### Arguments

`x` | The variant/tally `GRanges`.
`sample.id` | Unique ID for the sample in the VCF.
`project` | Description of the project/experiment; will be included in the VCF header.
`genome` | `GmapGenome` object, or the name of one (in the default genome directory). This is used for obtaining the anchor base when outputting indels.

### Details

A variant `GRanges` has an element for every unique combination of position and alternate base. A `VCF` object, like the file format, has a row for every position, with multiple alternate alleles collapsed within the row. This is the fundamental difference between the two data structures. We feel that the `GRanges` is easier to manipulate for filtering tasks, while `VCF` is obviously necessary for communication with external databases and tools.

Normally, despite its name, VCF is used for communicating genotype calls. We are calling variants, not genotypes, so we have extended the format accordingly.

Here is the mapping in detail:

- The `rowRanges` is formed by dropping the metadata columns from the `GRanges`.

- The `colData` consists of a single column, “Samples”, with a single row, set to 1 and named `sample.id`.

- The `exptData` has an element “header” with element “reference” set to the `seqlevels(x)` and element “samples” set to `sample.id`. This will also include the necessary metadata for describing our extensions to the format.

- The `fixed` table has the “REF” and “ALT” alleles, with “QUAL” and “FILTER” set to `NA`.

- The `geno` list has six matrix elements, all with a single column. The first is the mandatory “GT” element, the genotype, which we set to `NA`. Then there is “AD” (list matrix with the read count for each REF and ALT), “DP” (integer matrix with the total read count), and “AP” (list matrix of 0/1 flags for whether whether REF and/or ALT was present in the data).

### Value

A `VCF` object.

### Note

This function is DEPRECATED. The `callVariants` function now returns a `VRanges` object that can be coerced to a `VCF` object via `as(x, "VCF")`.

### Author(s)

Michael Lawrence, Jeremiah Degenhardt

### Examples

    ## Not run:
    vcf <- variantGR2Vcf(variants, "H1993", "example")
    writeVcf(vcf, "H1993.vcf", index = TRUE)

    ## End(Not run)

[Package VariantTools version 1.26.0 Index]