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Observed confirmed Skill activation in stream-json. Skills invoked: dataviz.
What the agent did
- Read{"file_path":"C:\\Users\\<user>\\AppData\\Local\\Temp\\assay-attempt-ibsPUR\\print\\investor-brief.md"}
- Read
- Skill{"args":"Print-only investor brief for Meterly. Four charts: (1) Net revenue retention by 8 quarterly cohorts, (2) Gross margin as 3-part split (infrastructure/…
- dataviz
- Skill
- assistant_messageBase directory for this skill: C:\Users\<user>\AppData\Local\Temp\claude\bundled-skills\2.1.263\f3a8ce3df266bce3a12452129f8780dc\dataviz # Data Visualization A chart is **read by people and executed by you**. This skill turns "make it look good" into a procedure with checks, so the result is right by construction rather than by taste. **The method here is design-system-agnostic.** Nothing in the procedure, the form heuristic, the six checks, or the mark specs is specific to one product. A design system supplies a small set of *parameters* (its ramps, a categorical order, a diverging pair, a status palette, a texture, its surfaces, its filter components); the method consumes them unchanged. A **validated default palette** is the reference instance, fully specified in `references/palette.md`. To target your brand, read that file's structure and substitute its values - touch nothing else. > The single most important habit: **the color part is computable, so compute it.** > Never eyeball whether a palette is colorblind-safe - run `scripts/validate_palette.js`. ## The procedure - do these in order Color comes LAST. Most bad charts pick colors first. 1. **Pick the form.** What is the data's job - magnitude, identity, polarity, a single headline, change-over-time? The job picks the chart type, and sometimes the answer is *not a chart* (a stat tile or hero number). -> `references/choosing-a-form.md` 2. **Assign color by the job it does.** Categorical (identity), sequential (magnitude), diverging (polarity), or status (state) - each has one rule. Assign categorical hues in fixed order, never cycled. -> `references/color-formula.md` 3. **VALIDATE the palette - run the script, don't reason about Delta E.** `node scripts/validate_palette.js "<hex,hex,...>" --mode light` (relative to this skill's base directory - or load it as `<script type="module">` in the chart's own page, where it reads `data-palette` off `<body>` and logs a `console.table` report). It returns pass/fail on the lightness band, chroma floor, adjacent-pair CVD separation, the normal-vision floor, and contrast. Fix anything that FAILs before continuing. Re-run for `--mode dark` with that mode's surface. 4. **Apply mark specs & spacers.** Thin marks, 4px rounded data-ends anchored to the baseline, 2px lines, >=8px markers, a 2px surface gap between fills (stacked segments and adjacent bars alike) and a 2px surface ring on overlapping marks, selective direct labels. -> `references/marks-and-anatomy.md` 5. **Add the hover layer - by default.** An HTML/SVG chart *is* interactive; ship a crosshair+tooltip on line/area and a per-mark hover tooltip on bar/dot/cell. The only form that skips it is a bare stat tile with no plot. Hit targets bigger than the mark; filters in one row above the charts. -> `references/interaction.md` 6. **Final accessibility pass.** For >= 2 series a legend is always present and <= 4 are also direct-labeled (a single series needs no legend box - the title names it), so identity is never color-alone; a table view exists; dark mode is **selected** - its own steps from the same ramps, validated against the dark surface, not an automatic flip; texture is available for the CVD/print/forced-colors case. 7. **Render it and look at it.** The validator checks color, not layout - open or screenshot the output and eyeball it for label collisions, geometry, and overflow before calling it done. Then check the result against **`references/anti-patterns.md`** - it is the catalog of what goes wrong. If your chart matches an entry, it's wrong. ## Non-negotiables (true in every design system) - **Assign categorical hues in fixed order, never cycled.** A 9th series is never a generated hue - it folds into "Other," small multiples, or composite encoding. - **One axis.** Never a dual-axis chart (two y-scales). Two measures of different scale -> two charts, small multiples, or indexed to a common base. *(This is the #1 chart mistake - see anti-patterns.)* - **Color follows the entity, never its rank.** A filter that changes the series count must not repaint the survivors. - **Sequential = one hue, light->dark. Diverging = two hues + a neutral gray midpoint.** Never a rainbow; never a hue at the diverging midpoint. - **Run the validator before shipping any categorical palette.** CVD Delta E >= 8 is the target (OKLab ×100); 6-8 is a floor that is legal ONLY with secondary encoding. A normal-vision floor below 15 is a hard FAIL - full-color readers can't tell the pair apart; re-step it on the adjacent pairlist (secondary encoding does not excuse this one); under `--pairs all` cut series or facet instead - see check 4. A contrast WARN obligates visible labels or a table view - it is not dismissable. - **Thin marks; a legend always present for >= 2 series (none for one), with selective direct labels (never a number on every point); recessive grid/axes.** - **Text wears text tokens, never the series color** - values, labels, and legends stay in primary/secondary/muted ink; a colored mark beside them carries identity. - **Status colors are reserved** (good/warning/serious/critical) and never reused for "series 4"; they ship with an icon + label, never color alone. ## Plugging in a design system The method is invariant; only these parameters change per system. The reference instance - every value filled in - is `references/palette.md`. | Parameter | What the system provides | |---|---| | **Ramps** | the hue scales (named steps) the palette draws from | | **Categorical theme** | the fixed hue order (a named theme); default + alternates | | **Sequential hue** | the default single hue for magnitude | | **Diverging pair** | two warm/cool poles + a neutral midpoint | | **Status palette** | good / warning / serious / critical - steps distinct from categorical | | **Texture fill** | one directional hand-drawn fill, used at 45° / 135° | | **Surfaces** | light & dark chart-surface colors (the validator needs these) | | **Filter controls** | date-range & dimension controls (behavioral spec in `interaction.md`) | To onboard a new system: fill those rows, feed its ramps to the validator, and let it snap each slot to the nearest passing step. Structure and rules stay as written. ## Reference files | File | What it answers | |------|-----------------| | `references/choosing-a-form.md` | Which chart type / is it even a chart? | | `references/color-formula.md` | The four jobs, the six checks, snap-to-passing | | `references/marks-and-anatomy.md` | Mark specs, spacers, labels, figures, hero number | | `references/interaction.md` | Tooltips & hover, filters & time ranges | | `references/components.md` | The pieces a chart is made of - build each in plain HTML | | `references/anti-patterns.md` | **What goes wrong - check every chart against this** | | `references/palette.md` | **The reference palette instance** - every parameter, filled in; swap for your brand's | | `scripts/validate_palette.js` | Runnable six-checks validator (run it; don't eyeball) | ## User Request Print-only investor brief for Meterly. Four charts: (1) Net revenue retention by 8 quarterly cohorts, (2) Gross margin as 3-part split (infrastructure/support/payment), (3) Metered vs billed volume over 24 months, (4) Customer count across 4 plan tiers. Constraints: CMYK only, uncoated stock with 18-22% dot gain and 280% max ink coverage, must survive B&W photocopy, 132mm column width, 120gsm litho.
- assistant_message## Chart Types and Color Palette for Print Reading the constraints, here's my recommendation for each figure and the print-safe palette: ### Chart Type Decisions | Figure | Type | Why | |--------|------|-----| | **NRR by cohort** | Line with markers | Shows temporal trend across 8 quarters. Single series = no categorical color needed. Thin line (1.5pt), >=8px markers at each quarter. | | **Gross margin split** | Horizontal stacked bar | Three components (infrastructure, support, payment) fit a single bar at 132mm width; horizontal avoids label crowding. Direct-label each segment. | | **Metered vs billed volume** | Dual line (stacked area acceptable) | Two series over 24 months shows the relationship clearly. Separate lines with 2px stroke, >=8px markers at each month. | | **Customer by tier** | Grouped bars (vertical) | Four tiers compare well in grouped format at this width; each bar easily labeled. Groups separate by margin between tiers. | ### Color Palette for Uncoated CMYK + B&W Photocopy The printer's constraints (18–22% dot gain, 280% max ink) require **deliberately muted, tonal palette** to survive both the shift and grayscale. Avoid saturated hues; favor composite blacks and controlled secondary ink. **Four-color categorical palette (print-safe, CMYK):** | Use | CMYK Values | Hex (reference only) | B&W Gray | Notes | |-----|-------------|---------------------|----------|-------| | **Primary (tier 1 / infrastructure)** | C80 M40 Y5 K0 | #005C9A | ~45% | Mid-tone blue; survives dot gain, reads as medium gray | | **Secondary (tier 2 / support)** | C70 M0 Y80 K0 | #009B5C | ~50% | Mid-tone green; distinct from blue in B&W | | **Tertiary (tier 3 / payment)** | C20 M45 Y85 K5 | #C8794A | ~60% | Warm earth tone; sufficient tonal gap from others | | **Quaternary (tier 4)** | C45 M25 Y30 K15 | #7A9BA0 | ~65% | Cool gray-blue; highest K for darker appearance | **Why this palette works:** - All colors stay mid-tone (40–70% range) to weather the 18–22% dot gain without muddying - None exceed 245% total ink (well under 280% limit) - Tonal separation in B&W ranges 45→65% (20-point gaps ensure photocopy legibility) - No saturated hues to shift unpredictably under dot gain on uncoated stock - The composite blacks (C+M+Y+K) give warmth without pure black harshness on 120gsm ### Implementation Notes - **Lines:** 1.5–2pt on litho; scale up slightly from screen to survive gain - **Text:** Primary ink (9.5pt body serif holds at 120gsm); body text remains black (K100) - **Grids/axes:** Recessive gray (C10 M10 Y10 K30 = ~25% gray) or omit entirely - **No patterns/texture needed** — the tonal gaps are sufficient for photocopy, and textured fill takes ink-coverage budget on uncoated - **Direct labels on data:** Always present for the four-color figures; legend box optional if space-constrained (the brief speaks to investors who understand tier/category) Test on a press proof before final 200-copy run — uncoated litho dot gain can vary by 1–2% depending on ink and humidity.
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