type: task id: GRAPH_LIBRARY-RESEARCH_TEMPORAL_AXIS_GROUPING_FOR_WEEKLY_TICKS_AND_MONTHLY_LABELS title: Research temporal axis grouping for weekly ticks and monthly labels description: Investigate how Vega-Lite and Dataface should support temporal axes where dense weekly ticks remain visible but higher-level month labels are shown as grouped or centered interval labels. milestone: m1-ft-analytics-analyst-pilot owner: data-viz-designer-engineer status: not_started priority: p2

Research temporal axis grouping for weekly ticks and monthly labels

Superseded (2026-03-27). This narrowly scoped follow-on was consolidated into Consolidate semantic chart defaults and rendering control-surface follow-ons so the active backlog carries one M2 umbrella task instead of many M1 leaf items. Keep the notes below as reference detail, not as a separately scheduled task.

Problem

Investigate how Vega-Lite and Dataface should support temporal axes where dense weekly ticks remain visible but higher-level month labels are shown as grouped or centered interval labels.

Context

During M1 structure-lab work, a recurring temporal-axis problem emerged:

the chart may contain weekly data points or weekly bars
we may want to keep the weekly tick rhythm visible
but we do not want to label every week
instead, we may want month labels that summarize or group the weekly cadence

The visual intent is not just "fewer labels." It is a richer temporal axis where:

fine-grained weekly ticks still establish cadence and rhythm
coarser month labels act like grouped interval labels
those month labels may need to feel centered across the span of weeks they cover, not pinned to a single weekly tick

This task is specifically a research task. The goal is to understand:

what Vega-Lite already supports natively for this kind of axis treatment
whether the right solution is a single axis, layered axes, or custom labeling
what the cleanest Dataface integration path would be if we want this behavior

Relevant files and references:

dataface/core/render/chart/presentation.py
dataface/core/render/chart/standard_renderer.py
dataface/core/render/chart/DESIGN.md
examples/playground/faces/labs/m1-structure-bars-lines-lab.yml
follow-on temporal semantics task: ./add-temporal-axis-label-semantics-for-point-vs-interval-positioning.md

Note: - m1-structure-bars-lines-lab.yml was a March 26, 2026 session artifact from the parallel codex/m1-structure-lab branch. If it is not present on main, treat it as historical context and recreate the repro in a fresh playground face.

Possible Solutions

Vega-Lite can do it natively with one axis. This would be ideal if Vega-Lite already supports distinct tick cadence and grouped/coarser labels on the same axis in a straightforward way.
Vega-Lite can do it with layered/composed axes. This is likely if the solution requires one axis for weekly ticks and another overlaid axis for month labels or boundary annotations.
Dataface would need custom axis augmentation on top of Vega-Lite. This may be necessary if native Vega-Lite support is incomplete or too awkward.
Recommended: research Vega-Lite first, then document the smallest viable implementation path for Dataface. The main research question is whether Vega-Lite already has a native pattern for different date grouping and label positioning on the same axis, especially for weekly ticks with monthly labels centered across spans.

Plan

Inspect Vega-Lite's documented temporal-axis features relevant to: - time units - tick cadence - label cadence - multi-level or layered axes - band/interval positioning
Compare those capabilities against the desired weekly-tick / monthly-label behavior.
Identify whether the solution is: - fully native - native but awkward - or requiring Dataface-side composition
Record examples and a recommended integration path for DFT.
Link the result back to the broader temporal-axis semantics work.

Implementation Progress

Not started.

March 26, 2026 notes:

This task was opened from structure-lab critique while looking at weekly/temporal labeling semantics.
The main design question is not merely label density; it is grouped temporal labeling and whether labels should be centered over the spans they summarize.

QA Exploration

N/A for now. This is a research task.

[ ] QA exploration completed (or N/A for non-UI tasks)

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