Trendlines
Learn how crypto trendlines are constructed, including anchor selection, logarithmic vs linear scale, false precision, breaks and practical limitations.
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Trendlines connect selected swing points to visualise the slope and pace of a move. Because the line depends on anchor selection, chart scale and wick-versus-close conventions, it is best treated as a contextual guide rather than a mathematical barrier.
Core concept
An ascending trendline typically connects two or more selected swing lows; a descending trendline connects selected swing highs. The line is then extended forward as a visual reference for the slope of the existing move.
Unlike a horizontal support/resistance level, a trendline changes price as time passes. This makes the result sensitive to the chart scale and anchor points. On assets with very large percentage moves, a logarithmic chart and a linear chart can produce materially different lines through the same history.
How a trendline is constructed
1 · Choose chart scale
Linear scale gives equal vertical distance to equal price changes; logarithmic scale gives equal distance to equal percentage changes.
2 · Select meaningful anchors
Use a consistent swing rule and state whether anchors are based on wicks or closes.
3 · Project the slope
Extend the line forward without moving the original anchors to make later price fit.
4 · Test later interaction
Observe whether later reactions organise around the line or whether it loses relevance.
What to inspect
| Dimension | Question | Why it matters |
|---|---|---|
| Anchor quality | Are the points major swings or convenient minor pivots? | Poor anchors create arbitrary slopes. |
| Scale | Linear or logarithmic? | Large percentage moves can materially change the line. |
| Later touches | Does price interact with the projected line without redrawing it? | Additional reactions can support relevance but do not prove future behaviour. |
| Break quality | Wick, close, displacement and acceptance beyond the line. | A minor cross can be noise, especially on lower timeframes. |
| Horizontal structure | Did price also break an important swing high/low? | A trendline break alone is weaker evidence than broader structural failure. |
Worked example: linear vs logarithmic
Suppose BTC rises from £40,000 to £80,000 over several months. That is a 100% increase. A linear chart treats each £10,000 vertical step equally, while a logarithmic chart treats percentage changes equally.
A later candle may therefore break a linear trendline drawn through early swing lows while remaining above the logarithmic line through the same general structure. This is not a contradiction—it shows that the visual conclusion depends on the scale model.
If the same move also breaks a major horizontal higher low, that separate structural event carries information beyond the trendline slope itself.
Accelerating trends and multiple lines
Strong trends often accelerate. Analysts may draw a primary long-term trendline and later a steeper secondary line. Price can break the steeper line while remaining above the original slower line and while the HH/HL structure remains intact.
This is one reason a trendline break should be phrased carefully. “The accelerated slope has failed” is more precise than “the uptrend is over” if the wider structure has not broken.
Conversely, repeatedly drawing progressively shallower lines after every failure can become narrative preservation. If the line no longer organises price, retire it instead of forcing another fit.
Common mistakes and misunderstandings
- Redrawing a trendline after every breach to preserve the preferred narrative.
- Ignoring the effect of logarithmic versus linear scale.
- Treating two convenient points as objective proof of a trend.
- Assuming a trendline break equals a horizontal market-structure reversal.
- Using different wick/close anchor conventions within the same line.
Knowledge checkpoint
Q1. Why can linear and logarithmic trendlines disagree?
Q2. What makes anchor selection vulnerable to hindsight bias?
Q3. Why is a trendline break not the same as breaking a major swing low or high?
Q4. When should a trendline be retired rather than redrawn?
FAQ
❓ How many touches make a valid trendline?
There is no universal number. Two points define a line; later interactions can add evidence of relevance.
❓ Should trendlines use wicks or closes?
Either convention can be used if it is applied consistently.
❓ Is logarithmic scale better for crypto?
It is often useful over large percentage moves, but the appropriate scale depends on the analytical purpose.
❓ Does breaking a trendline reverse the trend?
No. It shows price crossed a projected slope; broader swing structure may remain intact.
Summary
- Trendlines are projected visual references built from selected anchors.
- Anchor choice, wick/close convention and chart scale introduce subjectivity.
- Do not redraw lines simply to preserve a preferred narrative.
- A trendline break can mean the slope changed without the broader trend reversing.
- Compare trendline behaviour with horizontal swing structure.
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