JOURNAL · 18 MAR 2026
Choosing a length without copying the neighbour’s chart
The first mark on our sheets is a sentence about what the average is meant to ignore. The number follows the sentence.
A shorter moving average stays near the closes and crosses them often. A longer one stays smoother and stands farther from small bends. Neither length is the academy’s house number. The margin of the sheet has to hold a sentence before it holds a figure: this line is meant to ignore moves shorter than a week, or shorter than a month, or whatever interval the student actually looks at.
In March a shopkeeper from Bang Sao Thong arrived with a 5-period line copied from a cousin’s notebook. He checks prices on Sunday night. A line that jitters with every daily close was giving him five alarms and no picture. Niran had him rewrite the margin: ignore anything that does not last a week of sessions. The 5 came off. A longer simple average went on. The sheet got quieter because his calendar was quieter.
Copying a length can still be a useful drill, if you copy it on purpose. Evening 2 asks everyone to compute the same short window so the arithmetic is shared. That length is a teaching device. It is not a recommendation for the share you follow at home. When the shared drill is over, the margin sentence returns, and the lengths are allowed to differ down the table.
Exponential averages do not escape the same question. The weighting changes how quickly the line notices a new close. It does not choose the horizon for you. Malai still asks for the sentence first, then the length, then the choice of simple or exponential. Students who start with the formula usually cannot say what they hoped the line would hide.
If you are marking charts alone, keep the rejected lengths in the margin rather than erasing them. The record of what you refused is part of the method. A clean page with a fashionable number and no sentence is how the cousin’s notebook started.