Connected scatterplot
A scatterplot whose points are joined by a line in a meaningful sequence — usually time. The reader sees the trajectory through 2D space, not just where points cluster.
The demo plots the US Phillips curve, 1960 → 1980, with
annual (inflation, unemployment) pairs joined in chronological
order. The 1960s sit in the lower-left in the classic downward
trade-off; the 1970s stagflation shock punches the line out
toward the upper-right (both axes climbing together) — the
empirical observation that broke Keynesian consensus and
powered Milton Friedman's natural-rate theory.
Source: Phillips curve — Wikipedia
Public surface
let plot = Plot::new(quarterly)
.mark(Mark::Line {
interpolation: Interpolation::Linear,
marker: Some(PointStyle::Circle),
})
.encode(plot::x("inflation", ScaleKind::Linear))
.encode(plot::y("unemployment", ScaleKind::Linear))
.encode(plot::order("quarter_index"))
.encode(plot::color("decade"));The minimum recipe: a line mark with markers on, X and Y both
Linear, and an order encoding that names the sort column.
Order encoding
Encoding::Order sorts each series's rows by the named
numeric column before line-segment emission. Without it, rows
are connected in DataFrame insertion order — fine for already-
sorted time series, wrong for shuffled input. Always set it when
your reader expects the line to follow time.
Continuous-X line vs band-X line
The Plot facade detects the X scale kind and routes:
X ScaleKind | Layout | Use case |
|---|---|---|
Linear / Log / Time | Continuous numeric axes | Connected scatter, time-series |
Band (default) | Categorical bands at centres | Standard line chart, e.g. quarterly |
Same Mark::Line mark; different X scale picks the right
projection automatically.