Freyja Documentation
Freyja is a tool to recover relative lineage abundances from mixed SARS-CoV-2 samples from a sequencing dataset (BAM aligned to the Hu-1 reference). The method uses lineage-determining mutational “barcodes” derived from the UShER global phylogenetic tree as a basis set to solve the constrained (unit sum, non-negative) de-mixing problem.
Freyja is intended as a post-processing step after primer trimming and variant calling in iVar (Grubaugh and Gangavaparu et al., 2019). From measurements of SNV freqency and sequencing depth at each position in the genome, Freyja returns an estimate of the true lineage abundances in the sample.
To ensure reproducibility of results, we provide old (timestamped) barcodes and metadata in the separate Freyja-data repository. Barcode version can be checked using the freyja demix --version command.
Usage: