flow

Applies a pipeline of operators to the chart's data. Operators partition, position, and transform the data before the mark draws it.

from gofish import chart, spread, stack, rect

chart(seafood).flow(
    spread(by="lake", dir="x"),
    stack(by="species", dir="y", label=False),
).mark(rect(h="count", fill="species")).render(w=500, h=300, axes=True)

Signature

ChartBuilder.flow(*operators) -> ChartBuilder

Parameters

Parameter	Type	Description
*operators	Operator	One or more operators, applied left to right

Returns a new ChartBuilder with the operators appended.

How it works

Operators run in order. Each one receives the data (or groups) produced by the previous one. In the example above:

1. spread(by="lake", dir="x") splits the rows into one group per lake and places the groups across the x axis.
2. stack(by="species", dir="y") stacks each lake's rows by species along y.

The mark then draws every leaf row.

Available operators

Operator	Purpose
spread	Lay groups out along an axis, with gaps
stack	Stack groups edge-to-edge along an axis
table	Lay groups out in a 2D grid
scatter	Position groups by x/y fields
group	Wrap each partition in a frame
derive	Transform the data with a Python function
log	Print the data for debugging

Notes

• flow() can be called multiple times; operators accumulate.
• A chart with no flow() draws a single mark over the whole dataset.