Evaluate trendline geometry before trusting a breakout

Score the slope before the close

A close through a drawn slope can look like a finished decision. The archive workflow read a later close through the line as a warning of possible trend change, not as proof that the trend had already flipped.

Editorial reading: treat the drawn slope as a testable hypothesis first. How the line is anchored, how often and how far apart price meets it, how long it has lasted, and how steep it appears on a fixed chart scale all change how much weight that close-beyond event deserves.

Draw the line on the outside of the path

Declining slopes are anchored on successive minor highs. Advancing slopes are anchored on successive minor lows. That construction is an external trendline: a slope anchored on successive distinct minor highs or minor lows without cutting through the body of the price path. A later close through that line can then be read as a warning of possible trend change.

Slopes drawn through the interior of the bar path, including those that ignore one-session spikes, are crossed too often to serve as change warnings. That construction is an internal trendline, and the evaluation excluded those interior lines.

Match the chart scale to the working method

A semilog scale, logarithmic price with linear time, was preferred when large vertical moves would compress earlier structure on an arithmetic scale. The chart scale should match the analyst's working method.

Apparent steepness depends on chart aspect ratio. With aspect held fixed, slope was better judged in coarse shallow, neutral, and steep bands than in exact degrees.

How the sample defined a line and a breakout

The evaluation used 199 advancing and 210 declining lines on equities from mid-1991 to mid-1996. Interior lines were excluded. A close-beyond breakout, a session close on the far side of the slope, was required as the breakout and was the event that started the measured subsequent swing. That later swing was taken to the ultimate swing extreme: the farthest high or low after the close-beyond event before a reversal of at least 20 percent.

A trendline touch was a distinct minor high or low that met or approached the slope. The breakout point was not counted as a touch, and only lines with at least three such touches were used. Touch spacing is the average time between counted touches, compared around a sample median near a month of sessions.

What followed the close in that bull-market window

In that bull-market window, a close below an advancing line was followed by a continued decline 38 percent of the time, while a close above a declining line was followed by a continued advance 69 percent of the time. A pierce was treated as a warning that still needed confirming tools.

Which line traits lined up with larger later swings

After a close through the line, subsequent measured swings were larger when touches were more widely spaced than the sample medians of 28 days on advancing lines and 29 days on declining lines, and when line length from first touch to breakout exceeded the sample medians of 137 and 139 days.

Grouping by touch count left advancing lines with only a small difference in the later decline, 16 percent at four or fewer touches versus 18 percent above four. Declining lines with more than four touches showed a larger later advance, 48 percent, than those with four or fewer, 35 percent.

With chart aspect held fixed, shallower lines were associated with larger subsequent swings than steeper ones.