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Thresholds

Color chart elements by whether values pass or fail a target. Supported on Line, Area, and clustered Bar charts via the threshold= prop.

Quick start

from dl2_reports import Line, Threshold

row.add(Line("performance", x_column="Week", y_columns=["Score"],
             threshold=Threshold(value=80, mode="above",
                                 blend_width=8, apply_to="both")))

Threshold parameters

Plain dicts with the same keys are accepted; the shape validates mode and apply_to at construction.

Parameter Type Default (viewer) Description
value float (required) The threshold to compare against.
pass_color str #22c55e (green) Color for passing values.
fail_color str #ef4444 (red) Color for failing values.
mode str 'above' 'above': values ≥ threshold pass. 'below': values ≤ threshold pass. 'equals': only exact matches pass.
show_line bool True Draw a reference line at the threshold value.
line_style str 'dashed' Reference line style: 'solid', 'dashed', 'dotted'.
blend_width float 5 Width of the color blend zone at crossings, as % of chart width (0–50). Line/area only.
apply_to str 'both' 'both', 'markers' (only markers get threshold colors), or 'lines' (only lines/areas do).

Per-visual behavior

Visual Behavior
Line Line segments colored with gradient blending at crossings; markers colored by value.
Area Fill and stroke colored with gradient blending; markers by value.
Clustered bar Each bar colored by its own value. (Not available on stacked bars.)

Gradient blending (line/area)

blend_width controls how gradually colors transition at a crossing:

  • 0 — hard edge at the crossing point
  • 5 — subtle blend (default)
  • 10–15 — visible, gradual fade

Multi-series tip

With several series, full threshold coloring makes lines indistinguishable. Use apply_to="markers" to keep distinct series colors and show pass/fail on the markers only:

Line("sales", x_column="Quarter",
     y_columns=["Electronics", "Clothing", "Home"],
     threshold=Threshold(value=4000, mode="above", apply_to="markers"))

Related

  • Annotations — a yAxis line is a lighter-weight target marker with no recoloring.
  • Gauge ranges — banded targets for single values.
  • KPI breach_value/warning_value — status coloring for single values.