Sankey

Sankey diagrams draw one node per distinct endpoint and one ribbon per flow, with each ribbon’s thickness proportional to its value. Best for showing how a quantity divides and moves between two sets of things: order statuses across years, traffic channels into outcomes, or one step of a user journey into the next.

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Fields

A sankey needs exactly three fields, picked on the Fields tab:

• Source — a dimension (a time dimension works too, labelled by its grain). The node a flow leaves.
• Target — a dimension. The node a flow enters.
• Value — a measure. Each row’s value becomes one ribbon’s thickness.

Each result row is read as one flow, so a query grouped by two dimensions with one measure draws directly. Swap exchanges the source and target, which reverses every ribbon’s direction. Stages come from shared node names rather than from a stage field: rows A → B and B → C draw as a three-stage diagram, because B appears as both a target and a source. Two dimensions that share no values always draw two stages. A row with a blank endpoint, or a value of zero or less, is not a flow and is left out — a sankey cannot draw a ribbon with no thickness. Cyclic data is rejected rather than drawn. A flow that returns to a node it already passed through has no left-to-right layout, so the chart names the loop and asks you to remove one hop.

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Node grouping

A wide breakdown can return more flows than a diagram can carry, and the small ones become unreadable first. Node grouping folds them into a single Other node per side, so the tail stays represented as an aggregate instead of vanishing. It is off until you pick a mode, in the Node grouping section of the Fields tab:

• Minimal share — fold every node below a percentage of its side’s total. A node sitting exactly on the threshold is kept.
• Top N nodes — keep the N largest nodes per side. Tied nodes at the cutoff are kept together, so asking for the top 3 can keep more than 3 when third place is shared.

The two sides fold independently, each against its own total, because a node that is small as a target may be large as a source. The bucket’s name is yours to set; leave it blank for Other. When both sides fold at once, the two buckets are named apart — Other (source) and Other (target) — so one is not read as the other. A single node is never folded on its own — replacing one named node with a same-sized Other would say less than leaving it alone. A node whose own value already matches the bucket’s name is also left out of the bucket, so a real category called “Other” is never merged into it. The bucket stands for a set of members rather than one, so it has no query behind it: clicking a ribbon that touches it does not drill down.

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Truncation

Independently of grouping, a sankey draws at most 50 flows, keeping the largest. This is a backstop against a runaway result, not a legibility control — when it removes anything, a warning appears beside the Flows heading on the Fields tab saying how many of the total it is showing, pointing at node grouping, which is the real answer for a diagram too wide to read.

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Data labels

Each node carries its name and, optionally, its value. Both are independent buttons in the Data labels section of the Style tab: Name is on by default, Value is off. With both on, the value follows the name in parentheses; with only the value on, the node carries a bare number; with both off the diagram draws no labels. A node’s value is the larger of its inflow and its outflow, and takes the value field’s own number format. Labels sit to the right of their node, except in the final stage, where they flip to the left so they stay inside the frame.

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Color

Each node takes its own color from the palette selected in the Palette dropdown on the Style tab. The color follows the node’s name rather than its position, so filtering or re-sorting the query does not repaint the diagram. See Palettes for the built-in palettes and how to define a custom one. The Flows control sets where a ribbon takes its color from:

• Source — the color of the node the ribbon leaves. The default.
• Neutral — one muted color for every ribbon, leaving the nodes to carry the palette.
• Target — the color of the node the ribbon enters.

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Tooltips

Hovering a ribbon shows the result columns named in Tooltip fields on the Fields tab, which starts as every column in the query except the three the diagram already draws — source, target and value. Add them back like any other field if you want them repeated. Hovering a node shows its name and value. See Tooltips for adding, removing and reordering fields.

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Drill down

Clicking a ribbon drills into the row behind that flow. Ribbons touching a grouped Other node are not clickable, since that node covers several members at once.