The cluster chart and the TPO profile share a data model: both aggregate traded or touched quantity by price, then derive a value area from a percentage input. The differences live in the row rule, in how sessions are split, and in whether profiles are allowed to merge.
01 Ticks per row and letter stacking
In a TPO profile, each period contributes one letter to every price row it touched. The row rule — how many ticks constitute one row — therefore controls both the resolution and the legibility. A row equal to the instrument tick size is the most detailed and usually the least readable; a row of two or three ticks is the ordinary compromise on liquid instruments.
| Row rule | Rows per point | Practical effect |
|---|---|---|
| 1 tick | 4 | Maximum detail, heavy text stacking |
| 2 ticks | 2 | Balanced detail and legibility |
| 4 ticks | 1 | Coarse shape, quiet sessions vanish |
Letter stacking is a rendering decision, not a data decision: the underlying touch record is identical whatever the row rule, so a profile can be re-rendered at a finer resolution without recomputing anything.
02 Value area derivation
The value area is the contiguous price range containing a configured share of the total, typically 70 %. ATAS walks outwards from the point of control, comparing the two adjacent rows at each step and extending towards the larger one. Two consequences follow.
- A tie between adjacent rows is broken by a fixed rule, so the value area is deterministic but not unique — a different platform may extend the other way.
- Changing the percentage by five points can move an edge by several rows on a compact profile and by one row on a stretched one.
The value area calculation is independent of the cluster mode used to draw the same instrument, so a delta cluster and a volume profile over the same window can disagree in appearance while agreeing in value area.
03 Session splitting and composite profiles
Splitting rules decide where one profile ends. Options include clock boundaries, session templates, and manual splits at a chosen bar. Composite profiles then merge several sessions into one picture. Merging is where most confusion originates, because a composite profile's value area is not an average of the components' value areas.
| Split mode | Composite behaviour |
|---|---|
| Session template | Each session contributes independently; merge recomputes totals |
| Clock boundary | Fixed length blocks; merge is exact and predictable |
| Manual split | Arbitrary windows; merge is only meaningful if windows are comparable |
04 Cluster overlay on the profile
A profile is often paired with a cluster overlay so that the exact prints forming a row are visible next to the aggregate. The overlay inherits the cluster mode of the panel, which means a change to the mode silently changes the meaning of a screenshot taken yesterday. Recording the mode alongside the profile input is the simplest defence.
Three values make a profile chart reproducible: the row rule, the value area percentage and the split mode. If a chart cannot be reproduced from those three plus the instrument and the date range, something else in the panel is overriding them.
05 Single prints, tails and edge cases
Single prints are rows touched by exactly one period. They are structurally important because they mark where the market moved quickly, but they are also the rows most affected by the row rule: merging two ticks per row merges two single prints into one, and the shape changes. Tails at the extremes of a profile are similarly sensitive.
Because of that sensitivity, a profile used for documentation should state its row rule explicitly. The same advice applies to the footprint bars described on the footprint chart configuration page, and to the replay sessions described in replay and data feeds.