wehub-resource-sync
131 lines
7.8 KiB
Markdown
131 lines
7.8 KiB
Markdown
<!--
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name: 'Skill: Data Visualization'
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description: Skill instructions for producing accessible, brand-neutral charts, graphs, dashboards, and data visualizations using a validated method
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ccVersion: 2.1.198
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-->
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---
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name: Data Visualization
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description: >
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Produce a chart, graph, dashboard, or any data visualization that reads as one
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system — elegant, accessible, and consistent in light and dark — BRAND-NEUTRAL,
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shipping a placeholder palette to swap for your own. Read this BEFORE generating
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ANY chart (bar, line, area, heatmap, scatter,
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sparkline, donut), choosing chart colors, building a stat tile / meter / KPI row,
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or laying out a dashboard. Teaches a design-system-AGNOSTIC method: a form
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heuristic, a color formula with a runnable validator, mark specs, and interaction
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rules. The method is invariant; a design system plugs in its own ramps and
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surfaces. A validated default palette is documented in `references/palette.md`
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— swap that file's values for your brand's. Triggers on: "chart", "graph", "plot", "data viz", "dashboard",
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"analytics", "visualize data", "categorical colors", "sequential / diverging
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palette", "stat tile", "sparkline", "heatmap", "legend", "axis", "tooltip",
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"chart colors", "color by series".
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---
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# Data Visualization
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A chart is **read by people and executed by you**. This skill turns "make it look
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good" into a procedure with checks, so the result is right by construction rather
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than by taste.
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**The method here is design-system-agnostic.** Nothing in the procedure, the form
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heuristic, the six checks, or the mark specs is specific to one product. A design
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system supplies a small set of *parameters* (its ramps, a categorical order, a
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diverging pair, a status palette, a texture, its surfaces, its filter components);
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the method consumes them unchanged. A **validated default palette** is the
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reference instance, fully specified in `references/palette.md`. To target your
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brand, read that file's structure and substitute its values — touch nothing else.
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> The single most important habit: **the color part is computable, so compute it.**
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> Never eyeball whether a palette is colorblind-safe — run `scripts/validate_palette.js`.
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## The procedure — do these in order
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Color comes LAST. Most bad charts pick colors first.
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1. **Pick the form.** What is the data's job — magnitude, identity, polarity, a
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single headline, change-over-time? The job picks the chart type, and sometimes
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the answer is *not a chart* (a stat tile or hero number). → `references/choosing-a-form.md`
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2. **Assign color by the job it does.** Categorical (identity), sequential
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(magnitude), diverging (polarity), or status (state) — each has one rule.
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Assign categorical hues in fixed order, never cycled. → `references/color-formula.md`
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3. **VALIDATE the palette — run the script, don't reason about ΔE.**
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`node scripts/validate_palette.js "<hex,hex,…>" --mode light` (relative to
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this skill's base directory — or load it as `<script type="module">` in the
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chart's own page, where it reads
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`data-palette` off `<body>` and logs a `console.table` report). It returns
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pass/fail on the lightness band, chroma floor, adjacent-pair CVD separation,
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and contrast. Fix anything that FAILs before continuing. Re-run for
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`--mode dark` with that mode's surface.
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4. **Apply mark specs & spacers.** Thin marks, 4px rounded data-ends anchored to
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the baseline, 2px lines, ≥8px markers, a 2px surface gap between fills (stacked
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segments and adjacent bars alike) and a 2px surface ring on overlapping marks,
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selective direct labels. → `references/marks-and-anatomy.md`
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5. **Add the hover layer — by default.** An HTML/SVG chart *is* interactive; ship
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a crosshair+tooltip on line/area and a per-mark hover tooltip on bar/dot/cell.
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The only form that skips it is a bare stat tile with no plot. Hit targets bigger
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than the mark; filters in one row above the charts. → `references/interaction.md`
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6. **Final accessibility pass.** For ≥ 2 series a legend is always present and ≤ 4
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are also direct-labeled (a single series needs no legend box — the title names
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it), so identity is never color-alone; a table view exists; dark mode is **selected** — its own
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steps from the same ramps, validated against the dark surface, not an automatic
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flip; texture is available for the CVD/print/forced-colors case.
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7. **Render it and look at it.** The validator checks color, not layout — open or
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screenshot the output and eyeball it for label collisions, geometry, and overflow
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before calling it done.
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Then check the result against **`references/anti-patterns.md`** — it is the catalog
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of what goes wrong. If your chart matches an entry, it's wrong.
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## Non-negotiables (true in every design system)
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- **Assign categorical hues in fixed order, never cycled.** A 9th series is never a
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generated hue — it folds into "Other," small multiples, or composite encoding.
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- **One axis.** Never a dual-axis chart (two y-scales). Two measures of different
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scale → two charts, small multiples, or indexed to a common base. *(This is the
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#1 chart mistake — see anti-patterns.)*
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- **Color follows the entity, never its rank.** A filter that changes the series
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count must not repaint the survivors.
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- **Sequential = one hue, light→dark. Diverging = two hues + a neutral gray
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midpoint.** Never a rainbow; never a hue at the diverging midpoint.
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- **Run the validator before shipping any categorical palette.** CVD ≥ 12 is the
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target; 8–12 is a floor that is legal ONLY with secondary encoding. A contrast WARN
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obligates visible labels or a table view — it is not dismissable.
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- **Thin marks; a legend always present for ≥ 2 series (none for one), with
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selective direct labels (never a number on every point); recessive grid/axes.**
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- **Text wears text tokens, never the series color** — values, labels, and legends
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stay in primary/secondary/muted ink; a colored mark beside them carries identity.
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- **Status colors are reserved** (good/warning/serious/critical) and never reused
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for "series 4"; they ship with an icon + label, never color alone.
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## Plugging in a design system
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The method is invariant; only these parameters change per system. The reference
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instance — every value filled in — is `references/palette.md`.
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| Parameter | What the system provides |
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|---|---|
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| **Ramps** | the hue scales (named steps) the palette draws from |
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| **Categorical theme** | the fixed hue order (a named theme); default + alternates |
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| **Sequential hue** | the default single hue for magnitude |
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| **Diverging pair** | two warm/cool poles + a neutral midpoint |
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| **Status palette** | good / warning / serious / critical — steps distinct from categorical |
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| **Texture fill** | one directional hand-drawn fill, used at 45° / 135° |
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| **Surfaces** | light & dark chart-surface colors (the validator needs these) |
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| **Filter controls** | date-range & dimension controls (behavioral spec in `interaction.md`) |
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To onboard a new system: fill those rows, feed its ramps to the validator, and let
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it snap each slot to the nearest passing step. Structure and rules stay as written.
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## Reference files
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| File | What it answers |
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|------|-----------------|
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| `references/choosing-a-form.md` | Which chart type / is it even a chart? |
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| `references/color-formula.md` | The four jobs, the six checks, snap-to-passing |
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| `references/marks-and-anatomy.md` | Mark specs, spacers, labels, figures, hero number |
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| `references/interaction.md` | Tooltips & hover, filters & time ranges |
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| `references/components.md` | The pieces a chart is made of — build each in plain HTML |
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| `references/anti-patterns.md` | **What goes wrong — check every chart against this** |
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| `references/palette.md` | **The reference palette instance** — every parameter, filled in; swap for your brand's |
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| `scripts/validate_palette.js` | Runnable six-checks validator (run it; don't eyeball) |
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