# Multiple Sequence Alignment Utilities

Functions to extract features from and to manipulate multiple sequence alignments (MSA).

Specialized Modules:

- Deprecated Interface for Multiple Sequence Alignment Utilities

  Defines

  VRNA_ALN_DEFAULT
    #include <ViennaRNA/sequences/alignments.h>

    Use default alignment settings.

  VRNA_ALN_RNA
    #include <ViennaRNA/sequences/alignments.h>

    Convert to RNA alphabet.

  VRNA_ALN_DNA
    #include <ViennaRNA/sequences/alignments.h>

    Convert to DNA alphabet.

  VRNA_ALN_UPPERCASE
    #include <ViennaRNA/sequences/alignments.h>

    Convert to uppercase nucleotide letters.

  VRNA_ALN_LOWERCASE
    #include <ViennaRNA/sequences/alignments.h>

    Convert to lowercase nucleotide letters.

  VRNA_MEASURE_SHANNON_ENTROPY
    #include <ViennaRNA/sequences/alignments.h>

    Flag indicating Shannon Entropy measure.

    Shannon Entropy is defined as \( H = - \sum_c p_c \cdot \log_2 p_c \)

  Typedefs

  typedef struct vrna_pinfo_s vrna_pinfo_t
    #include <ViennaRNA/sequences/alignments.h>

    Typename for the base pair info repesenting data structure vrna_pinfo_s.

  Functions

  int vrna_aln_mpi(const char **alignment)
    #include <ViennaRNA/sequences/alignments.h>

    Get the mean pairwise identity in steps from ?to?(ident)

    SWIG Wrapper Notes:

      This function is available as function `aln_mpi()`. See e.g. `RNA.aln_mpi()` in the Python API.

    Parameters:

      - alignment – Aligned sequences

    Returns:

      The mean pairwise identity

  vrna_pinfo_t *vrna_aln_pinfo( vrna_fold_compound_t *fc, const char *structure, double threshold)
    #include <ViennaRNA/sequences/alignments.h>

    Retrieve an array of vrna_pinfo_t structures from precomputed pair probabilities.

    This array of structures contains information about positionwise pair probabilies, base pair entropy and more

    See also

    vrna_pinfo_t, and vrna_pf()

    Parameters:

      - fc – The vrna_fold_compound_t of type VRNA_FC_TYPE_COMPARATIVE with precomputed partition function matrices

      - structure – An optional structure in dot-bracket notation (Maybe NULL)

      - threshold – Do not include results with pair probabilities below threshold

    Returns:

      The vrna_pinfo_t array

  int *vrna_aln_pscore(const char **alignment, vrna_md_t *md)
    #include <ViennaRNA/sequences/alignments.h>

    SWIG Wrapper Notes:

      This function is available as overloaded function `aln_pscore()` where the last parameter may be omitted, indicating `md` = `NULL`. See e.g. `RNA.aln_pscore()` in the Python API.

  int vrna_pscore( vrna_fold_compound_t *fc, unsigned int i, unsigned int j)
    #include <ViennaRNA/sequences/alignments.h>
  int vrna_pscore_freq( vrna_fold_compound_t *fc, const unsigned int *frequencies, unsigned int pairs)
    #include <ViennaRNA/sequences/alignments.h>
  char **vrna_aln_slice(const char **alignment, unsigned int i, unsigned int j)
    #include <ViennaRNA/sequences/alignments.h>

    Slice out a subalignment from a larger alignment.

    See also

    vrna_aln_free()

    Note

    The user is responsible to free the memory occupied by the returned subalignment

    Parameters:

      - alignment – The input alignment

      - i – The first column of the subalignment (1-based)

      - j – The last column of the subalignment (1-based)

    Returns:

      The subalignment between column \(i\) and \(j\)

  void vrna_aln_free(char **alignment)
    #include <ViennaRNA/sequences/alignments.h>

    Free memory occupied by a set of aligned sequences.

    Parameters:

      - alignment – The input alignment

  char **vrna_aln_uppercase(const char **alignment)
    #include <ViennaRNA/sequences/alignments.h>

    Create a copy of an alignment with only uppercase letters in the sequences.

    See also

    vrna_aln_copy

    Parameters:

      - alignment – The input sequence alignment (last entry must be NULL terminated)

    Returns:

      A copy of the input alignment where lowercase sequence letters are replaced by uppercase letters

  char **vrna_aln_toRNA(const char **alignment)
    #include <ViennaRNA/sequences/alignments.h>

    Create a copy of an alignment where DNA alphabet is replaced by RNA alphabet.

    See also

    vrna_aln_copy

    Parameters:

      - alignment – The input sequence alignment (last entry must be NULL terminated)

    Returns:

      A copy of the input alignment where DNA alphabet is replaced by RNA alphabet (T -> U)

  char **vrna_aln_copy(const char **alignment, unsigned int options)
    #include <ViennaRNA/sequences/alignments.h>

    Make a copy of a multiple sequence alignment.

    This function allows one to create a copy of a multiple sequence alignment. The `options` parameter additionally allows for sequence manipulation, such as converting DNA to RNA alphabet, and conversion to uppercase letters.

    See also

    vrna_aln_copy(), VRNA_ALN_RNA, VRNA_ALN_UPPERCASE, VRNA_ALN_DEFAULT

    Parameters:

      - alignment – The input sequence alignment (last entry must be NULL terminated)

      - options – Option flags indicating whether the aligned sequences should be converted

    Returns:

      A (manipulated) copy of the input alignment

  float *vrna_aln_conservation_struct(const char **alignment, const char *structure, const vrna_md_t *md)
    #include <ViennaRNA/sequences/alignments.h>

    Compute base pair conservation of a consensus structure.

    This function computes the base pair conservation (fraction of canonical base pairs) of a consensus structure given a multiple sequence alignment. The base pair types that are considered canonical may be specified using the vrna_md_t.pair array. Passing NULL as parameter `md` results in default pairing rules, i.e. canonical Watson-Crick and GU Wobble pairs.

    SWIG Wrapper Notes:

      This function is available as overloaded function `aln_conservation_struct()` where the last parameter `md` may be omitted, indicating `md` = `NULL`. See, e.g. `RNA.aln_conservation_struct()` in the Python API.

    Parameters:

      - alignment – The input sequence alignment (last entry must be NULL terminated)

      - structure – The consensus structure in dot-bracket notation

      - md – Model details that specify compatible base pairs (Maybe NULL)

    Returns:

      A 1-based vector of base pair conservations

  float *vrna_aln_conservation_col(const char **alignment, const vrna_md_t *md_p, unsigned int options)
    #include <ViennaRNA/sequences/alignments.h>

    Compute nucleotide conservation in an alignment.

    This function computes the conservation of nucleotides in alignment columns. The simples measure is Shannon Entropy and can be selected by passing the VRNA_MEASURE_SHANNON_ENTROPY flag in the `options` parameter.

    SWIG Wrapper Notes:

      This function is available as overloaded function `aln_conservation_col()` where the last two parameters may be omitted, indicating `md` = `NULL`, and `options` = VRNA_MEASURE_SHANNON_ENTROPY, respectively. See e.g. `RNA.aln_conservation_col()` in the Python API.

    See also

    VRNA_MEASURE_SHANNON_ENTROPY

    Note

    Currently, only VRNA_MEASURE_SHANNON_ENTROPY is supported as conservation measure.

    Parameters:

      - alignment – The input sequence alignment (last entry must be NULL terminated)

      - md – Model details that specify known nucleotides (Maybe NULL)

      - options – A flag indicating which measure of conservation should be applied

    Returns:

      A 1-based vector of column conservations

  char *vrna_aln_consensus_sequence(const char **alignment, const vrna_md_t *md_p)
    #include <ViennaRNA/sequences/alignments.h>

    Compute the consensus sequence for a given multiple sequence alignment.

    SWIG Wrapper Notes:

      This function is available as overloaded function `aln_consensus_sequence()` where the last parameter may be omitted, indicating `md` = `NULL`. See e.g. `RNA.aln_consensus_sequence()` in the Python API.

    Parameters:

      - alignment – The input sequence alignment (last entry must be NULL terminated)

      - md_p – Model details that specify known nucleotides (Maybe NULL)

    Returns:

      The consensus sequence of the alignment, i.e. the most frequent nucleotide for each alignment column

  char *vrna_aln_consensus_mis(const char **alignment, const vrna_md_t *md_p)
    #include <ViennaRNA/sequences/alignments.h>

    Compute the Most Informative Sequence (MIS) for a given multiple sequence alignment.

    The most informative sequence (MIS) [Freyhult et al., 2005] displays for each alignment column the nucleotides with frequency greater than the background frequency, projected into IUPAC notation. Columns where gaps are over-represented are in lower case.

    SWIG Wrapper Notes:

      This function is available as overloaded function `aln_consensus_mis()` where the last parameter may be omitted, indicating `md` = `NULL`. See e.g. `RNA.aln_consensus_mis()` in the Python API.

    Parameters:

      - alignment – The input sequence alignment (last entry must be NULL terminated)

      - md_p – Model details that specify known nucleotides (Maybe NULL)

    Returns:

      The most informative sequence for the alignment

  struct vrna_pinfo_s
    #include <ViennaRNA/sequences/alignments.h>

    A base pair info structure.

    For each base pair (i,j) with i,j in [0, n-1] the structure lists:

    - its probability ‘p’

    - an entropy-like measure for its well-definedness ‘ent’

    - the frequency of each type of pair in ‘bp[]’

      - ’bp[0]’ contains the number of non-compatible sequences

      - ’bp[1]’ the number of CG pairs, etc.

    Public Members

    unsigned i

      nucleotide position i

    unsigned j

      nucleotide position j

    float p

      Probability.

    float ent

      Pseudo entropy for \( p(i,j) = S_i + S_j - p_ij*ln(p_ij) \).

    short bp[8]

      Frequencies of pair_types.

    char comp

      1 iff pair is in mfe structure