Direct answer: worked example of trendline drawing
Trendline drawing is the process of fitting a straight line to chart price points that you choose to represent the “swing” of an uptrend or downtrend. A worked example makes the process verifiable by listing inputs (the points), stating the assumptions (what the chart scale means), and showing the calculations (slope and line equation) that produce the drawn line.
Mechanism or definition (what you are actually doing)
A simple trendline in a chart is usually a straight line in x–y coordinates:
- x = time position (for example, a candle index).
- y = a price value (for example, the high or low at a chosen pivot).
- Pivot points = selected chart points that you claim the trendline should connect (for an uptrend you often use lows; for a downtrend you often use highs).
Worked example setup (all assumptions stated):
- We assume a chart where each candle is 1 time unit apart.
- We assume we picked two pivot lows from a historical series and documented them as coordinates.
- We measure y in “price units” without converting to another scale.
- We ignore spreads, execution, and commissions because trendline drawing itself is a visual/geometry task.
Evidence or example: numerical scenario with full calculations
Step 1: Choose two documented pivot lows
Assume we chose two pivot lows on an uptrend:
- Pivot A: (x1, y1) = (2, 101.0)
- Pivot B: (x2, y2) = (6, 103.0)
Assumption: these pivots are the points that the trendline is intended to pass through.
Step 2: Compute the slope
Slope m of the line through the two points:
- m = (y2 − y1) / (x2 − x1)
- m = (103.0 − 101.0) / (6 − 2)
- m = 2.0 / 4
- m = 0.5 price-units per time unit
Step 3: Write the line equation
Using point A, the line is:
- y = y1 + m(x − x1)
- y = 101.0 + 0.5(x − 2)
- y = 101.0 + 0.5x − 1.0
- y = 0.5x + 100.0
So, the trendline drawn on the chart is the set of points (x, y) satisfying y = 0.5x + 100.0.
Step 4: Check how other points “fit” (verification within the example)
Assume you also recorded a third pivot low C at:
- Pivot C: (x3, y3) = (4, 102.1)
Compute the line’s expected y at x3:
- y_line at x=4 = 0.5(4) + 100.0 = 2.0 + 100.0 = 102.0
Compute the vertical deviation (difference in price units):
- deviation = y3 − y_line = 102.1 − 102.0 = +0.1
Interpretation (non-predictive): the third pivot is close to the line under the assumptions used. The same method can be applied to additional points to see whether they consistently fall near the line or whether the fit is inconsistent.
Limitations and risks (material failure modes)
- Point selection is not unique. Different pivot choices can produce different slopes. If two analysts pick different highs/lows, they may draw different “best” lines even with identical math.
- Chart scaling and definitions matter. If one chart uses candle highs/lows while another uses closes, the y-values change. Also, a “time unit” depends on timeframe (for example, 1 candle may represent different actual durations).
- Overfitting is possible. A line can be drawn to connect points exactly, but that does not mean the pattern is stable under small changes to inputs.
- The line is not a standalone signal. A drawn trendline describes geometry relative to chosen inputs; it does not, by itself, establish future outcomes.
Verification or next question (how to independently check)
To verify independently, repeat the exact process with the same documented inputs:
- Record the two pivots used to define the line (x1, y1) and (x2, y2).
- Recalculate slope m and the equation y = m x + b (or its equivalent form).
- For any additional points you want to test, compute the deviation from the line the same way as in the example.
A helpful next question is: Which pivot definition did you use (highs, lows, closes), and how sensitive is the line to changing those pivot choices?