Scoring {openPrimeR} | R Documentation

## Scoring Functions.

### Description

`score_degen`

  Determines the degeneration score of a sequence.

`score_conservation`

  Determines the sequence conservation scores of a set of templates using Shannon entropy.

`score_primers`

  Computes scores for a set of primers based on the deviations of the primers from the constraints.

### Usage

    score_conservation(template.df, gap.char = "-", win.len = 30,
      by.group = TRUE)

    score_degen(seq, gap.char = "-")

    score_primers(primer.df, settings,
      active.constraints = names(constraints(settings)), alpha = 0.5)

### Arguments

`template.df` | A `Templates` object providing the set of templates.
`gap.char` | The gap character in the sequences. The default is "-".
`win.len` | The size of a window for evaluating conservation. The default window size is set to 30.
`by.group` | Whether the determination of binding regions should be stratified according to the groups defined in `template.df`. The default is `TRUE`.
`seq` | A list of vectors containing individual characters of a nucleotide sequence.
`primer.df` | A `Primers` object containing the primers.
`settings` | A `DesignSettings` object containing the analysis settings.
`active.constraints` | A character vector of constraint identifiers that are considered for scoring the primers.
`alpha` | A numeric that is used to determine the trade-off between the impact of the maximal observed deviation and the total deviation. At its default `alpha` is set to 0.5 such that the maximal deviation and the total deviation have an equal weight when computing the penalties.

### Details

`score_degen` computes the degeneration of an ambiguous sequence by considering the number of unambiguous sequences that are represented by the the ambiguous sequence. Let a sequence `S` of length `n` be represented by a collection of sets such that

S = {s_1, s_2, …, s_n}

where s_i indicates the set of unambiguous bases found at position i of the primer. Then the degeneracy D of a primer can be defined as

D = ∏_i{|s_i|}

where |s_i| provides the number of disambiguated bases at position i.

`score_primers` determines the penalty of a primer in the following way. Let `d` be a vector indicating the absolute deviations from individual constraints and let `p` be the scalar penalty that is assigned to a primer. We define

p = α \cdot \max_i d_i + ∑_i (1 - α) \cdot d_i

such that for large values of `alpha` the maximal deviation dominates giving rise to a local penalty (reflecting the largest absolute deviation) and for small `alpha` the total deviation dominates giving rise to a global penalty (reflecting the sum of constraint deviations). When `alpha` is 1 only the most extreme absolute deviation is considered and when `alpha` is 0 the sum of all absolute deviations is computed.

### Value

A list containing `Entropies` and `Alignments`. `Entropies` is a data frame with conservation scores. Each column indicates a position in the alignment of template sequences and each row gives the entropies of the sequences belonging to a specific group of template sequences. `Alignments` is a list of `DNABin` objects, where each object gives the alignment corresponding to one group of template sequences.

`score_degen` finds the number of unambiguous sequences that are represented by `seq`.

`score_primers` returns a data frame containing scores for individual primers.

### Note

`score_conservation` requires the MAFFT software for multiple alignments (http://mafft.cbrc.jp/alignment/software/).

### Examples

    ## Not run:
    data(Ippolito)
    entropy.data <- score_conservation(template.df, gap.char = "-", win.len = 18, by.group = TRUE)

    ## End(Not run)
    # Compute degeneration for sequences with differing number of ambiguous bases
    seq <- strsplit(c("ctggaattacggtacc", "taggaaccggrtaagc", "rtaaasrygtar"), split = "")
    degen <- score_degen(seq)

    # Score the primers
    data(Ippolito)
    primer.scores <- score_primers(primer.df, settings)

[Package openPrimeR version 1.6.0 Index]