Chart Dashboard

Chart dashboard

Turn whatever information the user gives — a table, pasted numbers, a set of metrics, notes, or just a topic and some facts — into a single self-contained HTML page of SVG charts rendered with charts-lib: a dashboard, a report, or a slide deck.

Workflow

1. Extract the data. Pull every number, category, and time series out of the user's input into a short plan: for each planned panel note title, chart type, categories, series. If the user gave a topic with no numbers, say plainly that figures are illustrative and label them as such on the page. Never silently invent numbers that read as real measurements.

   Three things count as invention, and the last two are easy to miss:

   • Filling a gap. A missing week is a gap (null), not a zero — a zero draws a collapse that never happened. And a gap only reads as one if the series is unsmoothed: Charts.line defaults to spline, which drops nulls and draws an unbroken curve through the hole. Set type: 'line' on any series with an interior gap.
   • Estimating onto a real chart. If you interpolate or model a value, it does not belong as another point on the primary trend, however carefully you dash the line or footnote it. Readers remember the shape, not the caveat. Put estimates in their own panel, or leave the hole visible.
   • Rescaling stale numbers. When you're updating an existing page and the user gave you new figures for only some panels, label the rest as carried forward. Nudging last quarter's numbers so they look current is fabrication even though every individual figure came from somewhere real.

2. Pick the format by what the data has to say (see references/layout.md). The question is whether the page states a conclusion or lets the reader draw their own:

   • Dashboard — a monitoring surface. Panels stand on their own, the reader scans for what changed, and no prose tells them what to think. Use templates/dashboard.html. This is the right default when the user hands you metrics without an argument attached.
   • Report — an argument with evidence. Reach for it when the user is trying to convince someone ("write up", "for the board", "retrospective", "analysis"), or when they told you the conclusion themselves and the page exists to support it. Use templates/report.html.
   • Deck — an argument delivered by someone, one claim per slide, read from across a room or clicked through in a tab. Reach for it when the user says presentation, slides, deck, "present this", "walk them through it", or names a meeting the page has to survive. Use templates/slides.html.

   When it's genuinely ambiguous, ask yourself who reads it and whether you will be in the room. Nobody presents a bento grid to a board, and nobody watches a five-section narrative to see if last night's numbers moved. The deck is the one format that assumes a presenter: if the page has to stand alone with no one narrating, it is a report, however much the user said "slides".

3. Copy the template. It lives in this skill's own directory — resolve templates/ relative to the directory containing this SKILL.md, never from a hard-coded home path:

   <skill-dir>/templates/dashboard.html  →  ./index.html
   <skill-dir>/templates/report.html     →  ./index.html
   <skill-dir>/templates/slides.html     →  ./index.html
   

   Do not copy assets/charts-lib/ next to the output. The template's three charts-lib/… tags are placeholders; leave them exactly as written while you build the page, and fold the library in as the last step (step 9). Their order matters and the inliner preserves it — theme must load before charts.

4. Derive the structure from the findings, not from the template. The dashboard template deliberately ships with a placeholder two-cell grid, because any arrangement shipped there would end up on every page this skill produces. (Building a deck? The same rule, applied to slide order rather than grid cells: references/layout.md § Deck. The template shows one example of each of its eighteen layouts so the markup is visible in one place — that sequence is a catalogue, never a running order. Delete what the argument does not need.) Before writing markup, answer: what is the dominant shape of this analysis (one trend / a head-to-head comparison / a ranking / a funnel / a distribution / parallel equal measures / geography)? Is there genuinely one panel that is the reason the page exists? The answers pick the opening row — worked derivations for each shape are in references/layout.md § Compose the grid from the findings.

   Two checks before you move on. A hero must be earned: w8 h2 goes to a panel only when one finding dominates; co-equal measures get equal cells, and promoting one is a claim the data doesn't make. And if your top row came out as a wide line chart plus a donut plus a small panel, verify that it came from the data — that is the shape this skill falls into by reflex, and it is right only when a single trend really does lead and composition really is the second thing the reader needs.

5. Choose a chart per panel using references/chart-selection.md, then write the config against references/chart-api.md (the full charts-lib API: every factory, option, and theme token). Read that file before writing chart code — don't guess option names.

   For a single fact about one engine — what it refuses, whether it self-sizes, how many grid tracks it wants, its minimum readable size — read assets/charts-lib/charts.manifest.json instead of the whole API file. It is the same index the library carries as Charts.meta, kept in step with the code by the build, and it also holds the shared plotBox and grid rules.

   Check the chart's input contract first (chart-selection.md § Input contract). Each engine accepts a particular kind of x and y, and a mismatch is a broken panel rather than a style choice. The one that bites most often: a line chart needs an ordered x — dates, numbers, or labels that carry their own rising sequence ('Jan'…'Dec', 'Q1'…'Q4', 'Week 1'…'Week 12'). Named categories (regions, browsers, departments) render an error panel instead of a chart; use Charts.column when x is a name.

   Two more references come in at this step when they apply: write the panel titles against references/narrative.md (where a finding goes, and how to state it without editorializing), and if the page has a filter or dropdown, read references/controls.md before wiring it.

   When a panel marks something up — an intervention, a projection, a target, a labelled anomaly — read references/annotation.md for the cue and its mechanics. Colour and stroke are per-series on a line, so actual-vs- forecast is two series, not one styled midway.

6. If the user pointed at a brand — their site, a stylesheet, a screenshot, a set of hex codes — recolor to match, and change nothing else. Read references/theming.md and run the bundled extractor:

   node <skill-dir>/scripts/extract-theme.js <their-css-or-html>
   

   It harvests the design's canvas, series hue, and any color reserved for a utility role, then runs the same OKLCH recipe described in theming.md: paper, greyscale ink, a seven-step series ramp, and accent/annotation/ counter — taken from the design where it has a color that fits the role, derived by hue rotation where it doesn't. Apply its Charts.applyPalette block once, before the first chart call — hand it the palette and let theme.js re-derive the roles; assigning roles one by one leaves tiles, tooltips and dimmed legend keys on the old colours. Fix anything it marks FAIL rather than shipping it. Check the series hue it picked against what you know the brand's colour to be: the script ranks by how the CSS uses a colour, which usually finds the brand colour and occasionally promotes a heavily-used secondary instead. The report also names the design's typeface — reported, not applied, unless the page can genuinely load the face (see § One design system, only the colors change).

   If all you have is one brand color — a single hex, no CSS to harvest — run the same recipe with nothing observed:

   node <skill-dir>/scripts/generate-theme.js '#2323FF'
   

7. Verify before reporting done. The page still has its charts-lib/… placeholders at this point, so to run it you need the library beside it temporarily. Stage it — step 8 removes it again:

   node <skill-dir>/scripts/finalize.js index.html --stage
   

   Then use the strongest check your environment supports:

   • Browser tooling available — open the file, read the console for errors, and screenshot it to confirm layout. (In Claude Code: preview_start, then read_console_messages and a screenshot. Serve over a local HTTP server rather than file:// so the scripts execute.)
   • No browser tooling — run the bundled checker and fix what it reports:

     node <skill-dir>/scripts/check-page.js index.html
     

     It catches the four failures that do not throw and so survive a confident-looking build: a panel whose chart was never wired (an empty box), a line over unordered categories (an error panel inside the chart), a page still pointing at charts-lib/, and anything else that reaches the network. Each one reads as a styling bug rather than the missing wiring it is. Exit code is non-zero when something fails, so it also works as a gate. Run it here without --final — the page is not inlined yet, and mid-build that is simply where you are. (Step 8 runs it for you either way; running it now just shortens the loop.) Either way, fix any panel that renders empty or overflows its cell first. A panel reading "Line charts need a continuous or temporal x-axis" is the input-contract failure above — change the chart type or the x values, don't restyle it.

   If you built a deck, check it on paper too. It is made to be handed round as a PDF, and that path has failures the screen never shows: print to PDF (or open the print preview) and confirm one slide per sheet, nothing crossing a page edge, and the dark slides still dark. A slide whose content outgrew its frame is silently cropped there rather than scrolled.

   If the page has any control, test it. Change each dropdown to a non-default value and confirm — with a screenshot or by reading the rendered text back — that the affected charts redraw and that any action title recomputed with them. An untested filter is usually a broken filter.

8. Fold the library into the page, and ship one file. A dashboard outlives the folder it was written in — it gets emailed, dropped in Slack, committed to a wiki, opened from Downloads. A page that loads charts-lib/charts.js from a sibling folder renders as an empty grid the moment it travels alone, and it fails silently: the markup, the headings and the KPI numbers are all there, so it looks like a styling bug rather than a missing dependency. So the last build step replaces the three placeholder tags with the library's own contents. One command does the whole ending — checks the page as built, inlines the library, removes the staged copy, then re-checks with --final, which this time insists the page is standalone:

   node <skill-dir>/scripts/finalize.js index.html
   

   It stops before inlining if the build checks fail, since inlining a broken page only makes it a bigger broken page, and its exit code is the gate: a non-zero exit means you are not done. It removes a sibling charts-lib/ only when that folder holds exactly the three files it staged, so a folder of your own that happens to share the name survives. The result is one ~590 KB HTML file that opens over file:// with no server, no network, and no sibling folder. Some rules that follow from that:

   • Never reintroduce a <script src> or <link href> to anything. No CDN for a chart library, a font, an icon set, or a CSS reset — an offline reader, a locked-down laptop, or an air-gapped review gets a broken page. Web fonts are the common slip: name the family in the CSS stack and let it fall back to the system face, which is what the template already does.
   • Images go in as data: URIs or not at all.
   • The library is inlined verbatim. Don't minify it, don't strip the parts you think a page doesn't use, and don't hand-edit the inlined copy — a bug fixed in the page instead of in assets/charts-lib/ is lost on the next build. Rerunning finalize.js on an already-inlined file is a harmless no-op, so it is safe to re-run after edits.
   • If the user explicitly asks for the split form — they're checking the page into a repo beside other pages that share the library, say — skip finalize.js and keep the staged charts-lib/ next to the output, with the placeholder tags as the real references. Check that page with scripts/check-page.js index.html (no --final, which would fail it for the references it is supposed to have). That is the exception, not the default.

Rules that keep output good

• One idea per panel. A panel whose title needs "and" is two panels.
• Lead with the finding that matters most: if one trend is the reason the page exists, give it the wide top-left cell (w8 h2). If nothing dominates — three equally important measures, say — don't manufacture a hero; equal panels are the honest layout. The rest of the grid follows the same logic: the shape of the analysis picks the rows, and a layout reused from the last page is a layout that describes the last page's data (references/layout.md).
• Every panel gets a title and a subtitle that states units and scope ("USD thousands · Q4 2025"). Put units in yAxis.suffix and tooltip.valueSuffix too.
• A projection is never drawn in the same stroke as a measurement: dash the forecast (or scenario:'forecast' on bars) and name the notation in the subtitle. See references/annotation.md.
• Match the chart to what the data is, not to what looks good: a line only where x is time or a number, a donut/waffle only where the parts are non-negative and sum to one whole, a scatter only where both axes are measures. See chart-selection.md § Input contract.
• Order categorical bars by value, not alphabetically. Keep time on the x-axis left-to-right.
• Donuts stop being readable somewhere around six wedges — below a few percent the angles are indistinguishable and the reader is just reading the legend. Roll the tail into "Other", or use a ranked bar list if the tail is the point.
• Don't restate a series in two panels unless the second adds a new cut.
• Annotate what matters: callouts: [{ x, text }] on line charts for spikes, launches, and anomalies mentioned by the user.

How many charts? One per finding — no quota, no padding

The page is not a container to fill up. Each panel should answer a question the reader actually has, and the count falls out of the data rather than out of a target. Ask of every panel: what would the reader do differently after seeing this? If the answer is nothing, it isn't a panel.

That cuts both ways, and both failures are common:

• Padding. Given four numbers from an A/B test, the honest page is two or three panels and a plain statement of the lift. Filling a twelve-cell grid means inventing a donut of two nearly-identical sample sizes, a fabricated daily time series, a "by segment" split nobody measured. The moment you are reaching for something to chart, you have run past the end of the data — stop there. A small page that answers the question is a better deliverable than a full grid that pads it, even though the full grid looks more impressive at a glance.
• Compression. Given twenty measures that each carry a finding, don't force them into eight panels by stacking unrelated series onto shared axes. Let the page be long.

When there are only a few panels, widen them (w6/w8/w12) so the grid still reads as a designed page rather than a half-empty one — a two-panel dashboard is two big panels, not two small panels marooned top-left.

Reports work the same way: a figure exists because a claim in the prose needs evidence. A section that states no claim needs no chart, and a claim the reader will accept without proof doesn't need one either.

Fit the page to how it will be read

The dashboard and report templates are tuned for someone reading at a desk. When the user tells you otherwise — "I'm presenting this", "send it round", "print it" — the same page fails badly in that other context. Presenting is the case with its own template: a deck (templates/slides.html) is the right answer to "I'm presenting this", not a dashboard with the type scaled up. For the other two the fix is how much you put on the page and at what size, never a different design system. All three cases are in references/layout.md § Fit the page to how it will be read.

Make the chart show the finding, not just the data

Three defaults in charts-lib are deliberately plain, and taking them as-is is how a page ends up technically correct and useless. Override them on purpose:

• Emphasis. Read the title you just wrote. If it names specific categories, a specific series, or a specific moment — "the top two account for 90%", "Direct outperformed Partner", "the drop came after the March update" — the chart leaves categorical mode and enters emphasis mode: the subject takes the accent, everything else takes Charts.theme.muted. A finding stated in words above eight identical bars is a finding the reader has to re-derive.

  The mechanism differs by what the subject is — per-point color for categories, series color + lineWidth for one line among many, plotBands and callouts for a moment, a tinted centerText for a donut's focal wedge. All of them, plus the grouped-chart series-vs-cluster split, are in references/chart-selection.md § Emphasis. Three constraints hold across all of them: two colors, not a rainbow (multi-hue and an accent reads as no emphasis at all), at most 2–3 accented items (past that, go back to the full categorical palette), and muted still has to be readable — context bars are data too, which is why muted is derived at 3:1 against the canvas rather than picked for how quiet it looks.

  In a deck, emphasis mode is the exception and the plain ramp is the default. Not a different rule — the same one, biting harder: a deck is where the urge to make the point is strongest, and a grey supporting bar stops saying anything by the third slide that has one. Write no color unless the chart's own title names the points it means.

  Three standing rules that apply whether or not the chart is in emphasis mode: residual categories ("Other", "Don't know", a rolled-up tail) always take muted, since they can never be the finding; several context series take one identical mute rather than a ramp, so they read as a single band; and one emphasis per chart — an accented bar and a callout on that same bar is two competing signals, not double the emphasis.

• Status vs. emphasis. When a chart mixes measured, planned, and projected numbers, don't spend a palette color on the distinction — encode it in the fill with scenario: 'plan' | 'forecast' (outlined / hatched) and keep color for the finding. A projection drawn identically to a measurement is the same failure as inventing the number.

• Data labels. The library draws them in every chart type by default. Opt out with dataLabels: false where they'd collide — dense lines, many bars, grouped columns with 3+ series. See references/chart-selection.md § Data labels.

• Geofacet variant. 'bar' is what you get by typing nothing, which is not a reason to use it three times on one page. 'heat' when the spatial pattern is the point, 'gauge' when regions are measured against a shared target. See references/chart-api.md § Geofacet.

If you add a control, wire it

A dropdown that doesn't change the charts is worse than no dropdown: it reads as a broken page, and the reader stops trusting the numbers that are correct. So either add no controls at all — a static page is a perfectly good deliverable — or wire them completely, which means the data is filtered rather than the label, every dependent panel re-renders, and any action title recomputes from the same filtered rows. If the page has a control, read references/controls.md: it has the render(state) pattern in full, the guards to apply before shipping one, and the cases where small multiples beat a filter.

Legends go in one place

charts-lib puts the legend at the top, under the subtitle, and shows it automatically once a chart has two or more series or wedges. Leave it there. A reader scanning a grid of panels learns the legend's location once; a page where it sits above one chart, beside another and below a third makes them re-hunt for it every time, and that hunting is the entire cost of an inconsistent layout.

So: don't pass legend position options per chart, don't build legends in HTML next to the chart, and don't hand-place colored dots in a panel's corner. If a legend genuinely doesn't earn its space — single-series panels, or a donut whose wedges are already labelled by callouts — turn it off with legend: { enabled: false } for every panel in that situation, not just the cramped one. The only sanctioned alternative is charts-lib's own lineLabels: 'inline', and if you use it on one line chart, use it on all of them.

Put the finding in the title

A chart titled "Weekly throughput by site" makes the reader do the work of finding the point. A chart titled "Throughput fell 12% the week of the WMS cutover" hands it to them and then proves it underneath — the insight lives in the chart's own hierarchy, so it travels with the figure into a screenshot, a slide, or an email. The finding goes in title, the units and scope stay in subtitle.

The line that keeps this from becoming editorializing is whether the chart proves the sentence: "Billing drives 27% of all tickets" is measurable off the chart, "Billing is a serious problem" is a verdict the reader should reach themselves. When no single finding dominates, a plain descriptive title is the honest choice — don't manufacture a headline.

Read references/narrative.md before writing the titles. It has the write-this/not-this table, the length budget per cell, and the three-way choice between an action title, Charts.barInsightTable, and a soft surface card — including the rule that stops the same sentence appearing in two of them.

Nothing on the page that isn't data or its labels

• No invented narrative furniture that repeats what a chart already says: no "Key insight" banners, no "Executive summary" you wrote yourself, no highlighted takeaway strip across the top, no emoji, no "🚀".
• The header is title, one line of scope, and the reporting window. The footer is sources, definitions, and any honesty notes (illustrative figures, carried- forward panels, data-quality caveats). Nothing else belongs in either.
• Conclusions the user themselves stated ("the March spike is the thing I need to explain") belong on the relevant chart — as its title or a callout, in their framing — not restated as your own analysis in a banner.

One design system, only the colors change

Every visible component follows charts-lib's design language: its type scale, weights, spacing rhythm, stroke widths, hairlines, legend position and chart geometry. Those proportions are what make ten different chart types read as one family, and the page chrome inherits them so the cards don't look bolted on.

The colors are the exception, and the only exception. When a user supplies a brand, recolor via Charts.applyPalette — once, before the first factory call, never per chart — and let the page chrome pick those same values up from the sync block in the template. Corner radius may follow the brand too, since square vs. rounded is a brand signature the charts themselves don't express.

Do not introduce a second visual system on top: no custom card headers with their own type scale, no gradient hero panels, no shadows or borders the template doesn't already have.

Type is the one place where copying the brand usually backfires. Most brand faces are licensed webfonts you cannot load into a local file, and naming one in font-family just falls through to a system fallback you didn't choose — worse than keeping charts-lib's stack, which was picked to work at 11px in a chart. In a chart the cost is not only aesthetic: the engines measure label widths against the face they think they have, so a substituted one makes axis labels the engine had fitted collide. And a page that reaches for a webfont stops being standalone (step 8). Match the brand's font only when the face is genuinely available — a system font, or a file the user supplied. extract-theme.js reports the design's face and says outright whether it is loadable; when it isn't, keep the template stack and tell the user which face you couldn't use and why. Full method in references/theming.md.

The page has exactly five kinds of component, all already in the template: header, optional KPI row, chart panels, optional soft surface card (.note), footer. The KPI row exists because headline figures genuinely help — use the template's .kpi markup, which is sized off the chart type scale so the tiles look like they belong to the same page. Writing your own KPI strip with new CSS is the most common way this page ends up looking like two designs stapled together, and it is the thing to resist even though it feels helpful. A KPI tile is a label, a number, and at most one line of plain context — no arrows, no red/green verdicts, no "▲ 12% vs LY" badges.

If you find yourself writing new CSS classes, stop and ask whether a chart panel would carry the information better. Usually it would.

Output

One HTML file, standalone — no sibling charts-lib/ folder, no CDN tags, no network at open time (see step 8). A deck ships the same way, and a reader turns it into a PDF with their browser's own Print → Save as PDF: the template sets A4 landscape, one slide per sheet. Write it to the working directory (or where the user asked). Then surface it however your environment does that — attach or render the file if you can (in Claude Code: SendUserFile with display: "render"); otherwise print the absolute path and tell the user to open it in a browser. Either way, state which figures came from the user's data and which, if any, were illustrative.

Environment notes

Nothing in this skill requires a specific agent or vendor. It needs only the ability to read files from this directory, write an HTML file, copy a folder, and run Node (for finalize.js and the static checks). Without Node, inline the three library files by hand — paste charts.css into a <style> and theme.js then charts.js into <script> blocks, in that order, replacing the placeholder tags. Browser preview, screenshots, and file attachment are used when available and degrade gracefully when not.