resolve

Dereference reference columns into the drawn nodes they name. For each row, resolve matches the listed columns' values against the keyed nodes of from_ (a select_all(...) of a prior layer) and replaces each value in place with the matching node ref — a many-to-one join that preserves the row grain (no fan-out). It's the join that turns an edge or label table into something the chart can draw.

Pair it with .layer(table) to drive a tier from a second table, and with line(from_=, to=) (node-link edges) or ribbon(from_=, to=).

Node-link edges

from gofish import chart, scatter, resolve, select_all, circle, line

nodes = [
    {"id": "a", "grp": 0},
    {"id": "b", "grp": 1},
    {"id": "c", "grp": 1},
    {"id": "d", "grp": 2},
]
edges = [
    {"source": "a", "target": "b"},
    {"source": "a", "target": "c"},
    {"source": "b", "target": "d"},
    {"source": "c", "target": "d"},
]

chart(nodes).flow(scatter(by="id", x="grp", y="id")).mark(
    circle(r=14, fill="#4e79a7").name("nodes")
).layer(
    chart(edges)
    .flow(resolve(["source", "target"], from_=select_all("nodes")))
    .mark(line(from_="source", to="target", stroke="#888"))
).render(w=360, h=360)

Signature

resolve(cols, *, from_, key=None) -> Operator

Parameters

Dereference reference columns into the drawn nodes they name (resolve(cols, { from, key? })).

Option	Type	Default	Description
cols	list		Required. Local columns holding references to resolve in place.
from_	str		The selectAll(layerName) of a prior layer whose nodes the columns are matched against.
key	str		Explicit match field; defaults to the producing operator's by.

from_ carries a trailing underscore because from is a reserved word in Python; the JavaScript API spells the same option from. Returns an Operator for use inside .flow().

Semantics

• Many-to-one — each reference resolves to exactly one node (the match field must be a key); the row grain is preserved, no rows are added.
• In place — the matched columns are replaced by node refs, so a downstream mark reads them directly (line(from_="source", to="target")).
• Default key — when key is omitted, the match field is the one the from_ nodes were grouped by (scatter(by="id") ⇒ match on id). If those nodes were grouped by a function (no field name), pass an explicit key.
• Errors — a reference with no matching node throws, naming the column and value, rather than silently dropping the row.

resolve vs. derive

derive runs an opaque row transform; resolve is the specific, named case of joining reference columns against a drawn layer and replacing them with refs that read each node's post-layout position.