Sports Visualization

Sports Visualization

Outcome

Create the smallest reproducible figure that answers a defined question without exaggerating the evidence. Every important figure states its period, sample size, metric definition, grain, and relevant baseline. Add uncertainty when the claim depends on noisy differences.

This skill constructs figures. Use anti-slop-analytics for an independent keep/fix/kill review and results-reporting for the surrounding narrative.

When to use this skill

Use for exploratory distributions, coverage plots, model diagnostics, calibration, ratings and form trajectories, team or player comparisons, walk-forward results, and publication figures. Do not start with chart type: start with the question and the unit represented by each mark.

Required inputs

• question and intended audience;
• user-owned data or metrics artifact;
• sport, competition, grain, natural key, and period;
• relevant denominator, filters, and missing-data rules;
• metric definition and direction;
• comparison baseline and uncertainty artifact when applicable;
• desired output path and reproduction context.

If the source is a screenshot or rounded report table, do not reconstruct precise data unless explicitly labeled approximate. Prefer the underlying table.

Workflow

1. State the single claim or diagnostic question.
2. Validate input grain, keys, columns, types, and duplicated events.
3. Define what one mark, line, bar, or interval represents.
4. Choose the smallest chart that makes the comparison direct.
5. Add sport, population, period, denominator, units, and baseline.
6. Check axes, transforms, aggregation, bins, smoothing, missingness, and ordering.
7. Add uncertainty or fold spread if the claim compares noisy quantities.
8. Export the image and preserve the plotting command or code.
9. Write a one-sentence factual interpretation and one limitation.
10. Run an anti-slop pass before using the figure in a public claim.

Plot selection catalog

Read references/plot_catalog.md when routing a question to a chart. Read references/honest_labels.md before finalizing titles, captions, annotations, and uncertainty language.

Encoding defaults

For rates, the axis must show changes without manufacturing drama. Zero is not mandatory for every line plot, but any restricted range must be justified and clearly labeled. Bar length encodes magnitude and normally needs a meaningful zero.

Sports-specific caveats

• Team-game panels often contain complementary home and away rows. A home-win figure should filter is_home == 1; state unique-game n.
• Rolling features and ratings must be plotted as of the prediction timestamp, not after the event update.
• Unequal games played, minutes, plate appearances, or attempts can make player and team rates incomparable. Show opportunity thresholds or uncertainty.
• Schedule strength, postseason selection, neutral venues, overtime, ties, and rule changes can alter apparent trends.
• Season facets may have different lengths and missing weeks. Do not connect discontinuous observations as though spacing were equal.
• Calibration bins need event counts. A smooth-looking curve from small bins is not strong evidence.
• Fold-level model charts must retain losing folds and compare the same held-out rows.

Honest title and caption template

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Title: <quantity> by <comparison> — <sport/competition>, <period>
Subtitle/caption: n=<games/events/rows>; grain=<grain>; <metric definition>;
baseline=<reference>; uncertainty=<method or unknown>; exclusions=<important filters>.
Source: <artifact>; reproduce: <script/command>.

Use descriptive titles such as “Held-out log-loss by season” rather than conclusion titles such as “Model Dominates.” Put interpretation in the caption, bounded by the observed population.

Uncertainty and aggregation

• Use intervals appropriate to the sampling/design assumptions; name the method.
• When repeated teams, players, or games induce dependence, avoid pretending rows are independent. Consider grouped resampling or fold variation.
• Distinguish an unweighted season mean, an event-weighted mean, and a pooled metric. Label whichever is plotted.
• Do not invent error bars when only aggregate numbers exist. State uncertainty as unavailable and show the raw fold or season values.
• Show both numerator and denominator for important rates when feasible.

Hard constraints and integrity rules

1. Period and denominator appear on every key figure.
2. Metric, units, sport, population, and grain are explicit when not obvious.
3. A comparative claim includes its relevant baseline.
4. Axes and transforms do not manufacture the effect.
5. Dual-axis correlation theater is prohibited.
6. Probabilities are displayed as uncertain quantities, not destiny.
7. Training metrics are never labeled held-out or walk-forward.
8. Losing folds, missing periods, and excluded groups are not silently removed.
9. Every claim-bearing figure has a reproduction path.
10. Unknown uncertainty is disclosed, not fabricated.

Anti-patterns

• rainbow spaghetti with every team unlabeled;
• decorative 3-D, pie, gradients, or gauges;
• one hot streak presented as season truth;
• a correlation heatmap without a question;
• missing baseline in a model-comparison chart;
• smoothed lines with no method or window;
• in-sample fit presented as validation;
• cropped axes used to magnify small home-field changes;
• image exports with no source data or command.

Standalone helpers

Install pandas and matplotlib; Parquet also needs pyarrow or fastparquet. The table helpers accept user-owned CSV, Parquet, JSON, JSONL, or NDJSON.

For a team-game panel with is_home and point_diff:

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python <path-to-sports-visualization>/scripts/plot_home_margin_hist.py \
  --input games.csv --out home_margin.png

For a panel with season, is_home, and binary won:

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python <path-to-sports-visualization>/scripts/plot_home_win_rate.py \
  --input games.parquet --out home_rate.png

Column flags map alternate schemas. The home-win helper drops rows without an observed season/outcome, labels each season's eligible home-row denominator, uses a 0-to-1 rate scale, and displays 95% Wilson intervals. Those intervals treat eligible games as Bernoulli observations and do not account for broader season/team dependence.

For a JSON report containing a folds array, each row needs an explicit fold label, held-out denominator (n_test by default), and candidate and baseline metric fields:

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python <path-to-sports-visualization>/scripts/plot_walkforward_metrics.py \
  --json metrics.json \
  --fold-col fold \
  --metric logistic_log_loss \
  --baseline constant_log_loss \
  --out comparison.png

The helper rejects duplicate fold labels and missing/nonpositive denominators, but cannot verify that the two metric columns came from identical rows or derive sampling uncertainty from aggregate scores. Perform the row-identity check before plotting; its default title labels uncertainty unavailable.

Worked examples

Home win rate

Validate the panel is team-game grain, filter home rows, count unique contests, and show per-season rate with denominator. Caption the figure as “home rows only” and disclose ties or excluded games.

Walk-forward model comparison

Plot candidate and baseline on the same y-axis for every eligible fold. State that lower log-loss is better, retain folds where the candidate loses, and use a table instead if small differences are difficult to read honestly.

Team rating trajectories

Plot ratings recorded before each event update. Label a small number of relevant teams directly, mark long inactivity gaps, and avoid interpreting a rating line as causal player or coaching impact.

Output contract

Return the figure path, source artifact, plotting command/code, purpose, population and grain, period and denominator, metric/baseline, uncertainty method, important exclusions, one bounded interpretation, and remaining limits.

Resources

• references/plot_catalog.md — read when choosing the visual form for a sports question.
• references/honest_labels.md — read when writing titles, captions, denominators, and uncertainty notes.
• scripts/plot_home_margin_hist.py — standalone home-margin distribution plot.
• scripts/plot_home_win_rate.py — standalone home-win-rate plot.
• scripts/plot_walkforward_metrics.py — standalone fold comparison plot.