demultiplex {DNABarcodes} | R Documentation

## Demultiplex a set of reads.

### Description

The function `demultiplex` takes a set of reads that start with a barcode and assigns those reads to a reference barcode while possibly correcting errors.

The correct metric should be used, with `metric = "hamming"` to correct substitution errors and `metric = "seqlev"` to correct insertion, deletion, and substitution errors.

### Usage

    demultiplex(reads, barcodes, metric=c("hamming","seqlev","levenshtein","phaseshift"), cost_sub = 1, cost_indel = 1)

### Arguments

`reads` | The reads coming from your sequencing machines that start with a barcode. For `metric = "seqlev"` please provide some context after the (supposed) barcode, at least as many bases as errors that you want to correct.
`barcodes` | The reference barcodes that you used during library preparation and that you want to correct in your reads.
`metric` | The distance metric to be used to assign reads to reference barcodes.
`cost_sub` | The cost weight given to a substitution.
`cost_indel` | The cost weight given to insertions and deletions.

### Details

Reads are matched to their correct reference barcodes by calculating the distances between each read and each reference barcode. The reference barcode with the smallest distance to the read is assumed to be the correct original barcode of that read.

For `metric = "hamming"`, only the first `n` (with `n` being the length of the reference barcodes) bases of the read are used for these comparisons and no bases afterwards. Reads with fewer than `n` bases cannot be matched.

For `metric = "seqlev"`, the whole read is compared with the reference barcodes. The Sequence Levenshtein distance was especially developed for barcodes in DNA context and can cope with ambiguities that stem from changes to the length of the barcode.

The Levenshtein distance (`metric = "levenshtein"`) is largely undefined in DNA context and should be avoided. The Levenshtein distance only works if the length both of the reference barcode and the barcode in the read is known. With possible insertions and deletions, this becomes an unknown. For this reason, we always calculate the Levenshtein distance between the whole read and the whole reference barcode without coping with potential side effects.

### Value

A vector of reference barcodes of the same length as the input reads. Each reference barcode is the corrected version of the input barcode.

### Note

Do not try to correct errors in barcodes that were not systematically constructed for such a correction. To create such a barcode set, have a look into function `create.dnabarcodes`.

### See Also

`create.dnabarcodes`, `analyse.barcodes`

### Examples

    # Define some barcodes and inserts
    barcodes <- c("AGGT", "TTCC", "CTGA", "GCAA")
    insert <- 'ACGCAGGTTGCATATTTTAGGAAGTGAGGAGGAGGCACGGGCTCGAGCTGCGGCTGGGTCTGGGGCGCGG'

    # Choose and mutate a couple of thousand barcodes
    used_barcodes <- sample(barcodes,10000,replace=TRUE)
    mutated_barcodes <- unlist(lapply(strsplit(used_barcodes,""), function(x) { pos <- sample(1:length(x),1); x[pos] <- sample(c("C","G","A","T"),1); return(paste(x,collapse='')) } ))

    show(setequal(mutated_barcodes, used_barcodes)) # FALSE

    # Construct reads (= barcodes + insert)
    reads <- paste(mutated_barcodes, insert, sep='')

    # Demultiplex
    demultiplexed <- demultiplex(reads,barcodes,metric="hamming")

    # Show correctness
    show(setequal(demultiplexed, used_barcodes)) # TRUE

[Package DNABarcodes version 1.17.0 Index]