41 lines
1.7 KiB
Markdown
41 lines
1.7 KiB
Markdown
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# Chart Selection
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Choose visuals based on the question, not on what is easiest to render.
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## Question to Chart Map
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| Question | Preferred chart | Notes |
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|----------|-----------------|-------|
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| How is a metric changing over time? | line chart | annotate structural breaks and missing data |
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| Which groups are highest or lowest? | sorted bar chart | keep a shared baseline |
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| How is the distribution shaped? | histogram or box plot | avoid average-only summaries |
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| Are two variables related? | scatter plot | show trend and outliers separately |
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| How do parts contribute to the whole? | stacked bar with totals | keep category count low |
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| Where are users dropping? | funnel chart | define the time window explicitly |
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| How do cohorts retain over time? | cohort table or heatmap | show cohort size alongside retention |
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## Default Rules
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- Bars start at zero unless there is a strong reason not to.
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- Show underlying counts next to percentages when denominators are small.
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- Prefer direct labels over legends when possible.
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- Use one chart per decision question, not one chart per available metric.
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## Visual Anti-Patterns
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- Pie charts with many slices -> comparisons become guesswork.
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- Dual-axis charts -> viewers infer relationships that are not there.
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- Cumulative-only charts -> hide recent deterioration or recovery.
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- Truncated bar axes -> exaggerate small differences.
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- Stacked areas with many categories -> impossible to compare layers.
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## Before Shipping a Chart
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Check:
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1. What decision question this chart answers.
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2. Whether the baseline is visible.
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3. Whether the grain and time window match the narrative.
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4. Whether annotations explain outages, launches, or missing data.
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5. Whether a table would be clearer than the chart.
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