Phase 2: Transformation

      ┌───────────┐       ┌────────────────────────────┐
      │ ImmunData │       │ AnnData / Seurat / TCRdist │
      └───────────┘       │ seur@meta.data / adata.obs │
            │             └────────────────────────────┘
            │                             │
            ├─────────────────────────────┘
            │
            ▼
   annotate_immundata()    ──── Import external annotations to ImmunData
            │
            ▼ 
     agg_repertoires()     ──── Aggregate repertoires
            │
            ▼ 
    filter_immundata()     ──── Filter receptors or repertoires
            │
            ▼ 
    mutate_immundata()     ──── Create or modify columns, compute statistics
            │
            │     ┌────────────────┐
            ├────►│ save / plot #1 │
            │     └────────────────┘
            ▼ 
   annotate_immundata()    ──── Annotate ImmunData with the computed statistics
            │
            │     ┌────────────────┐
            ├────►│ save / plot #2 │
            │     └────────────────┘
            │
            ▼
┌────────────────────────┐
│seur@meta.data[:] <- ...│ ──── Export ImmunData annotations
│    adata.obs = ...     │
└────────────────────────┘

Transformation is a loop of annotation → modification and computation → visualisation, always producing a new ImmunData while leaving the parent intact. That immutability is what turns every notebook into a reproducible pipeline.

1. Import external annotations to ImmunData:

   annotate_immundata() (or its thin wrappers annotate_barcodes() / annotate_receptors()) merges labels from Seurat/AnnData/TCRdist/anything that can be expressed as a keyed data frame to the main table, so each chain has a corresponding annotation.

2. Aggregate repertoires:

   Now that extra labels are present, you might regroup receptors, for example, by donor × cell-state.

3. Filter receptors or repertoires:

   filter_immundata() accepts tidy-verse predicates on chains, receptors, or repertoires.

4. Create or modify columns, compute statistics:

   On this step, you compute statistics per-repertoire or per-receptor, using input receptor features. There are several scenarios depending on what you try to achieve.

   1) use immunarch for the most common analysis functions. The package will automatically annotate both receptors/barcodes/chains (!) and repertoires (!!) if it is possible;

   2) simply mutate on the whole dataset using dplyr syntax, like compute edit distance to a specific pattern using mutate_immundata;

   3) more complex compute that requires a function to apply to values and is probably not supported by duckplyr.

5. Save / plot #1:

   Cache the ImmunData. Use ggplot2 to visualise the statistics, computed from ImmunData.

6. Annotate ImmunData with the computed statistics:

   annotate_immundata() (again) joins the freshly minted statistics back to the canonical dataset.

7. Save / plot #2:

   Save the ImmunData with new annotations to disk. Plot the results of analysis.

8. Export ImmunData annotations:

   Write the annotated data back to the cell-level dataset (Seurat / AnnData) for the subsequent analysis. Additionally, you could write the ImmunData itself to disk if needed.