Pipeline components for real-time virus analysis

Frequencies

Aims & Terminology:

The change in the frequency of mutations over time (mutation frequencies) and the rise and fall of defined clades (tree_frequencies) aid in understanding the evolution of influenza and other pathogens. These are seperate calculations but share terminology and are conceptually similar.

Terminology

  • pivots refer to a series of time slices (coded as a np.ndarray), with the frequency calculations being performed at each time point. Note that the keyword argument to estimate_tree_frequencies may be a float which is (internally) turned into such an array.

Mutation frequencies

Mutation frequencies are calculated for each nucleotide mutation and each amino acid mutation in process.seqs.translations.items()

How to call:

process.estimate_tree_frequencies() takes a number of keyword parameters: * min_freq {float} (default: 0.01)

  • stiffness {float} (default: 20.0)

  • inertia {float} (default: 0.0)

  • pivots {int | np.array} (default: 24)

If a float, then x pivots are evenly spaced along the time interval of the samples. Pivots may instead be spaced by a time slice over the analysis via pivots = get_pivots_via_spacing(), which uses the pivot_spacing config parameter.

  • region {string | tuple | list} (default: "global")

If region is a list, region[0] is the name (commonly an acronym) and region[1] is a list of regions (or a string for a single region) that is used to reduce the alignment in question by matching to seq.attributes['region']. If region is a string, the alignment is matched similar to above (both the name and the region refer to this) If region is None or "global" then all regions are analysed.

  • include_set {dict} (default: {})

Config parameters

  • estimate_mutation_frequencies {bool} (default: False)
  • pivot_spacing {float} necessary if you want to calculate pivots through get_pivots_via_spacing

Side Effects

  • process.mutation_frequencies {dict}

    • Keys: (region_name {str}, protein {str}) where proteins are nuc and those in process.seqs.translations.
    • Values: {dict}
    • Keys: {tuple} (pos {int}, mutation {str})
    • Values: {numpy.ndarray, same shape as pivots}
  • process.mutation_frequency_confidence same structure as above.

  • process.mutation_frequency_counts {dict}

    • Keys: {str} region name
    • Values: {numpy.ndarray, same shape as pivots} To check: is this not overwritten by each protein?!?

Saving / Restoring

Saving: After each call to estimate_mutation_frequencies progress is saved to a pickle in the processed directory.

Restoring: During the first call to estimate_mutation_frequencies, this pickle is loaded (if it exists) and subsequent calculations are skipped where possible (i.e. when the key exists). The pickle is deemed valid if the names of the sequences are identical.