Double Curve

The Double Curve, also known as an S-curve, is a four-point Bezier path that creates a smooth S-shaped transition across the chart. The curve flows from the first anchor through a middle inflection point and into the opposite direction toward the final anchor, creating a natural-looking reversal of curvature. It is called a double curve because it consists of two opposing curve halves joined at a single inflection point where the direction of curvature changes.

This tool is particularly useful for tracing corrective waves in Elliott Wave analysis (A–B–C patterns), visualizing alternating price structure, and highlighting S-curve reversals where price changes direction smoothly over time. The double curve captures the natural ebb and flow of price better than a single arc can — it models the full swing from one extreme to the other with a single inflection point. This makes it ideal for scenarios where price moves in one direction, retraces, then reverses again — the classic A–B–C structure.

Unlike the Curve tool which uses visible control handles for manual adjustment, the Double Curve computes its control points automatically from the four anchor positions, ensuring a smooth inflection at P2. This makes it quicker to draw for common S-curve scenarios while still allowing full repositioning of all four anchor points after placement. The automatic control point calculation ensures that the curve always maintains C1 continuity at the inflection point — the tangents match perfectly where the two halves join, creating an invisible seam.

The third point (P3) is not a user-placed anchor. It is computed automatically based on the positions of P1, P2, and P4 to create a balanced S-curve with appropriate curvature on both halves. If you need full manual control over curvature with visible handles, use the Curve tool instead. The Double Curve is optimized for speed and consistency in the most common S-curve scenarios where the auto-computed shape produces the desired result.

1. 1
   Select the Double Curve tool

   Click the Double Curve icon in the shapes toolbar. The cursor changes to a crosshair.
2. 2
   Set the start (P1)

   Click to place the first point at the beginning of the S-curve on the chart.
3. 3
   Set the inflection (P2)

   Click to place the second point where the curve should change direction.
4. 4
   Set the end (P4)

   Click to place the fourth point to complete the S-curve. The third point is computed automatically.
5. 5
   Fine-tune anchors

   Drag any anchor point to reshape the curve. The inflection at P2 adjusts the S-curve automatically.
6. 6
   Style the curve

   Adjust border color, width, style, and optional fill from the configuration panel.

• Corrective waves (ABC patterns) — trace Elliott Wave corrective structures with an S-curve. P1 = start of wave A, P2 = end of wave B (retracement), P4 = end of wave C. The S-curve naturally models the A–B–C shape with a single inflection at the retracement peak.
• S-curve reversals — highlight transitions where price changes direction smoothly rather than with a sharp V-turn. Common in rounding reversals on daily and weekly timeframes where the transition spans multiple sessions with gradual rotation.
• Alternating price structure — visualize up-down-up or down-up-down sequences in trending markets. The S-curve naturally models the alternating rhythm of price swings where each swing reverses direction from the previous one.
• Double-bottom and double-top formations — draw a connecting curve across the two troughs of a double bottom or the two peaks of a double top. The S-curve shows the retracement between the two extremes and highlights the neckline zone for breakout analysis.
• Complex corrective patterns — annotate flats, zigzags, and triangle patterns in educational charts and trading journals for clear visual communication of complex pattern structures to viewers.
• Impulse wave channeling — draw the corrective channel within an impulse wave. The S-curve traces the wave 2 or wave 4 correction within a five-wave sequence, showing the typical A–B–C shape of counter-trend moves that characterize corrections.
• Sine wave half-cycles — approximate one complete half-cycle of a sine wave from trough to peak or peak to trough. Two double curves can form a full sine wave cycle on the chart for cyclic analysis of commodity and FX markets.

The inflection point (P2) is the most critical anchor in a double curve. This is where the curve changes from one direction to the opposite — from concave to convex or vice versa. Placing P2 at the correct swing point is essential for an accurate S-curve. In an A–B–C corrective wave, P2 corresponds to wave B (the retracement), which is the turning point between wave A and wave C. Getting P2 exactly on the retracement extreme ensures the curve matches the price structure.

The automatic control point calculation uses the position of P2 to determine the curvature of both halves. If P2 is closer to P1, the first half is shorter and tighter. If P2 is closer to P4, the second half is shorter and tighter. For a balanced S-curve where both halves have similar curvature, place P2 roughly mid-way between P1 and P4 in both price and time. The inflection marker option adds a visual indicator at P2 to make the direction change point obvious at a glance.

• 1.Annotation tools guide — TradingView Help
• 2.Elliott Wave Principle — A.J. Frost and Robert Prechter
• 3.Technical Analysis of Financial Markets — John J. Murphy
• 4.Mastering Elliott Wave — Glenn Neely
• 5.The Geometry of Markets — Gann and financial geometry literature
• 6.Corrective Pattern Analysis — Elliott Wave reference