Line Interpolation

By default, line series connect data points with straight segments. The interpolation option enables smooth curve rendering while keeping markers, tooltips, and interactions attached to the original data points.

MonotoneMonotone

monotone uses a cubic spline that is monotone in x. The curve passes through every data point without introducing artificial extrema between adjacent points — a good default choice for most smooth line charts.

{
    type: 'line',
    interpolation: {type: 'monotone'},
}

CardinalCardinal

cardinal produces a cardinal spline. The tension parameter (0–1, default 0) controls how tightly the curve follows the control points: 0 gives a loose curve, 1 collapses it to straight segments.

{
    type: 'line',
    interpolation: {type: 'cardinal', tension: 0.5},
}

NotesNotes

• Curves pass through every original data point.
• monotone requires data points to be ordered monotonically by their x values.
• With cardinal and tension < 1, the curve can overshoot the data extrema between points. Such portions may be clipped at the plot boundary. Use monotone when preserving extrema is important.
• nullMode behavior is preserved: gaps and zero-fills are applied before interpolation.
• To disable interpolation explicitly, set interpolation: {type: 'linear'} or omit the option entirely.