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SKILL.md
npx skills add inference-sh/skills --skill data-visualization
Data visualization with chart selection, color theory, and annotation best practices. Covers chart types (bar, line, scatter, heatmap), axes rules, and storytelling with data. Use for: charts, graphs, dashboards, reports, presentations, infographics, data stories. Triggers: data visualization, chart, graph, data chart, bar chart, line chart, scatter plot, data viz, visualization, dashboard chart, infographic data, data presentation, chart design, plot, heatmap, pie chart alternative
npx skills add inference-sh/skills --skill data-visualization
Install the belt CLI skill:
npx skills add belt-sh/cli
Create clear, effective data visualizations via inference.sh CLI.
Requires inference.sh CLI (
belt). Install instructions
| Data Relationship | Best Chart | Never Use |
|---|---|---|
| Change over time | Line chart | Pie chart |
| Comparing categories | Bar chart (horizontal for many categories) | Line chart |
| Part of a whole | Stacked bar, treemap | Pie chart (controversial but: bar is always clearer) |
| Distribution | Histogram, box plot | Bar chart |
| Correlation | Scatter plot | Bar chart |
| Ranking | Horizontal bar chart | Vertical bar, pie |
| Geographic | Choropleth map | Bar chart |
| Composition over time | Stacked area chart | Multiple pie charts |
| Single metric | Big number (KPI card) | Any chart (overkill) |
| Flow / process | Sankey diagram | Bar chart |
Pie charts are almost always the wrong choice:
| Rule | Why |
|---|---|
| Always start Y-axis at 0 (bar charts) | Prevents misleading visual |
| Line charts CAN start above 0 | When showing change, not absolute values |
| Label both axes | Reader shouldn't have to guess units |
| Remove unnecessary gridlines | Reduce visual noise |
| Use horizontal labels | Vertical text is hard to read |
| Sort bar charts by value | Don't use alphabetical order unless there's a reason |
| Principle | Application |
|---|---|
| Max 5-7 colors per chart | More becomes unreadable |
| Highlight one thing | Grey everything else, color the focus |
| Sequential for magnitude | Light → dark for low → high |
| Diverging for positive/negative | Red ← neutral → blue |
| Categorical for groups | Distinct hues, similar brightness |
| Colorblind-safe | Avoid red/green only — add shapes or labels |
| Consistent meaning | If blue = revenue, keep it blue everywhere |
| Element | Rule |
|---|---|
| Title | States the insight, not the data type. "Revenue doubled in Q2" not "Q2 Revenue Chart" |
| Annotations | Call out key data points directly on the chart |
| Legend | Avoid if possible — label directly on chart lines/bars |
| Font size | Minimum 12px, 14px+ for presentations |
| Number format | Use K, M, B for large numbers (42K not 42,000) |
| Data labels | Add to bars/points when exact values matter |
| Step | What to Do | Example |
|---|---|---|
| 1. Context | Set up what the reader needs to know | "We track customer acquisition cost monthly" |
| 2. Tension | Show the problem or change | "CAC increased 40% in Q3" |
| 3. Resolution | Show the insight or solution | "But LTV increased 80%, so unit economics improved" |
| Technique | When to Use |
|---|---|
| Call-out label | Highlight a specific data point ("Peak: 320K") |
| Reference line | Show target/benchmark ("Goal: 100K") |
| Shaded region | Mark a time period ("Product launch window") |
| Arrow + text | Draw attention to trend change |
| Before/after line | Show impact of an event |
| Mistake | Problem | Fix |
|---|---|---|
| Pie charts | Hard to compare, always misleading | Use bar charts or treemaps |
| Y-axis not starting at 0 (bar charts) | Exaggerates differences | Start at 0 for bars, OK to truncate for lines |
| Too many colors | Visual noise, confusing | Max 5-7 colors, highlight only what matters |
| No title or generic title | Reader doesn't know the insight | Title = the takeaway, not the data type |
| 3D charts | Distorts data, looks unprofessional | Always use 2D |
| Dual Y-axes | Misleading, hard to read | Use two separate charts |
| Alphabetical sort on bar charts | Hides the story | Sort by value (largest first) |
| No labels on axes | Reader can't interpret | Always label with units |
| Chartjunk (decorative elements) | Distracts from data | Remove everything that doesn't convey information |
| Red/green only for color coding | Colorblind users can't read | Use shapes, patterns, or colorblind-safe palettes |
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