UltraPlot Figures

Use UltraPlot's public axes-level APIs and automation to produce figures that are scientifically honest, publication-ready, and easy for the user to maintain. Treat concise reproduction code as part of figure quality.

Release update checks

Before the normal workflow, resolve scripts/update_skill.py relative to this SKILL.md. Unless the user has prohibited network access, run it with the Python interpreter selected by the active environment rules and pass --auto.

• Automatic release checks are enabled by default and run at most once per local calendar day.
• Never download, install, or replace skill files during the check.
• For update_available, report the installed and latest versions, recommend updating, link the stable GitHub Release, and provide the returned copy-ready update request in the user's language. Continue the user's original task.
• Treat only published stable Releases as available updates; ignore drafts and prereleases.
• Do not perform an update unless the user explicitly requests it. For a later update request, preserve Git history and uncommitted changes for a Git worktree; back up an ordinary installation before replacement.
• Continue normally for disabled, skipped_checked_today, no_release, up_to_date, or check_failed.
• Respect ULTRAPLOT_FIGURES_UPDATE_CHECK=0 as an explicit local opt-out.

Retained task artifacts

Treat retained task files as a strict allowlist. Retain only:

• one independently runnable plotting entry script for each scientifically distinct figure, plus minimal local helper code only when it materially reduces real duplication;
• the requested final figure files; when formats are unspecified, retain PDF and PNG;
• only when substantive preprocessing is necessary, the preprocessing code and the final processed datasets semantically consumed by the plotting code.

A processed file is semantically consumed only when its values determine final marks, labels, layout, or export behavior. Reading a file only for validation, provenance reporting, logging, or an assertion does not make it a reproduction dependency. Every persisted preprocessing result must have a real figure consumer. Do not reread a validation-only file to make it appear necessary.

Do not retain copies of user-provided raw inputs, intermediate datasets, validation-only or exclusion tables, diagnostic renders, screenshots, logs, audit dictionaries, JSON reports, manifests, README files, environment files, caches, backups, or temporary files. Re-render corrections to the same final paths. Summarize material assumptions, deviations, and unresolved issues in the final response instead of creating another file.

For review-only work, do not create retained files unless the user asks for a revision. For revisions, preserve the existing workflow where practical and make the smallest maintainable change that satisfies the request.

Choose the workflow

1. Clarify the scientific comparison and intended message.
2. Inspect variables, units, observation level, groups, missing values, and whether the input is raw, processed, or already plot-ready.
3. Use a plot-only workflow when the input is scientifically plot-ready.
4. Add a preprocessing stage only when operations materially change the sample, observation unit, scientific values, or analytical result.
5. For geospatial data, also inspect source CRS, coordinate units, bounds, transform, resolution, orientation, and NoData metadata as applicable.

Substantive preprocessing includes sample-changing cleaning or filtering, joins, aggregation to a new observation level, normalization, derived scientific variables, model fitting, inferential statistics, uncertainty estimation, and analytical spatial transformations. Put these operations and their scientific input checks in the preprocessing script.

Display-only operations may remain in the plotting script when concise and transparent. These include an explicitly requested display subset, category and draw order, a reshape required only by the plotting API, bar positions, label formatting, axis limits, and simple descriptive values computed from the exact plotted rows. Do not create a preprocessing script merely because a pandas or xarray operation is used.

An EPSG:4326 transformation created only for final display may remain in the plotting script. Any transformed data used for measurement, comparison, statistics, or classification belong in preprocessing. Never overwrite source data with a display representation.

When preprocessing is necessary, write its final outputs before implementing the plotting script. Prefer the smallest number of coherent output datasets. Keep different observation grains separate when combining them would make the result harder to understand.

Maintainable code

Write delivered code for reproduction and maintenance, not to prove that QA ran.

• Keep the execution path straightforward: imports, meaningful constants, data loading, minimal validation, plotting, formatting, saving, and entry point.
• Validate each scientific assumption once at the stage that owns it.
• In plotting code, validate only the fields and invariants required to render and interpret the figure. Do not recompute preprocessing results merely to confirm a processed table.
• Keep only processed columns and statistics used by the figure.
• Create a helper only when reused or when it isolates a genuinely non-trivial operation. Avoid one-line wrappers, pass-through abstractions, unused metadata, and configuration objects that merely rename local constants.
• Do not require a universal build_figure() function, dataclass, project structure, or helper module.
• Expose command-line arguments only for inputs, outputs, and parameters users are reasonably expected to change.
• Write comments for scientific rationale or non-obvious constraints, not to narrate ordinary code.
• Prefer pandas or xarray objects directly when they make data flow clearer.
• Keep rendering code in the plotting entry script by default. A parameterized entry script may generate a homogeneous series only when scientific meaning, layout, and processing logic are the same.

Scientific and output requirements

• Use public documented APIs. Confirm installed UltraPlot, matplotlib, and cartopy versions before relying on version-specific behavior. The validated baseline is UltraPlot 2.5.0, matplotlib 3.10.6, and cartopy 0.25.0.
• Match the encoding to the scientific question. Use perceptually uniform, colorblind-safe sequential maps for magnitude, diverging maps centered on a real neutral value for signed data, cyclic maps for phase or angle, and qualitative cycles for categories. Never use jet or rainbow for magnitude.
• Preserve honest baselines, observation units, spatial geometry, and uncertainty meaning. Do not silently discard observations or alter scientific values.
• Display geospatial distributions in EPSG:4326 with proj="pcarree" and degree-formatted longitude and latitude by default. Use another display projection only when the user or figure specification requests it. Use the original or scientifically appropriate projected data for calculations.
• Do not add or retain a figure-level or subplot-level title unless the user directly requests it. This restriction does not apply to axis labels, guide labels, annotations, panel identifiers, or genuine grid-edge structural labels.
• For two or more independent main Axes, use figure-local abc="a.", abcloc="ul" unless the user or journal requests another policy. Reserve the inner upper-left region and move ordinary annotations first.
• Use one consolidated format() call per coherent axes group. Mixed GeoAxes and CartesianAxes may require separate calls because they accept different keys.
• Treat the effective UltraPlot configuration as the style baseline. Prefer figure-local formatting, then bounded uplt.rc.context() changes. Do not use session-global or persistent rc changes for a single figure.
• Use exactly one physical width authority. Honor a requested journal= preset or total figwidth; otherwise use journal="nat2" (183 mm). Do not combine competing width authorities or approximate a journal preset.
• Unless the user, journal, or output specification requires an exact figure height, leave the total height unconstrained. When journal= or figwidth= fixes the width, do not also pass figheight=, figsize=, or call set_size_inches(). This preserves UltraPlot's ability to derive the height from the reference Axes, fixed data aspects, guides, and GridSpec geometry.
• Unless the user or journal specifies another value, define EXPORT_DPI = 1000 and pass it to every final fig.save(...) call. Use the same DPI for all requested formats and keep the default above 600 dpi.
• Do not use bbox_inches="tight" when exact physical size matters; it changes the saved canvas.

Layout and typography

Read references/layout.md before implementing a picture array, spanning subplot, mixed fixed- and auto-aspect layout, or unconstrained figure dimension, and whenever the first render has unexplained whitespace, misalignment, clipping, or overlap.

• Use the smallest grid that represents the intended topology. Use picture arrays only for genuine spans, holes, or non-rectangular topology, and use wratios and hratios for relative column and row sizes. Do not add duplicate grid rows or columns solely to make a subplot wider or taller.
• Use one UltraPlot GridSpec, compatible axis sharing, and the subplot that should genuinely govern automatic sizing. Preserve fixed data aspects.
• Keep UltraPlot's own tight layout active. For complex layouts, pass tight=True or confirm that the effective rc["subplots.tight"] is True.
• The first render with final data, labels, annotations, panel identifiers, and guides must omit left, right, top, bottom, space, wspace, hspace, outerpad, innerpad, panelpad, wpad, and hpad.
• Do not categorically prohibit explicit spacing. After a failed automatic render, classify the defect and retain only the smallest scoped override. Leave unaffected sequence entries as None so they remain automatic.
• Do not use fixed margins or spacing to repair ordinary-annotation collisions, incorrect limits, fixed-aspect slot waste, unsuitable ratios, a wrong refnum, or an infeasible topology.
• Never combine UltraPlot auto layout with Matplotlib tight_layout(), constrained_layout, or subplots_adjust().
• Use an axes-level guide for one Axes and a figure-level guide only when the encoding is genuinely shared.

Preserve the effective UltraPlot font configuration by default. For Chinese text, append Microsoft YaHei to the ordered font.family fallback list unless the user or journal specifies another font. Resolve it before figure creation and register its .ttf, .ttc, or .otf file if necessary. Verify required glyphs in vector and raster output.

Implementation sequence

Inspect the input and choose the data flow. If substantive preprocessing is needed, implement and run it first. Then load only plot-ready data, perform minimal plotting-input checks, create and format the figure, save directly to the final requested paths, and verify internally. Use references/recipes.md for concise starting patterns; do not treat any recipe as a mandatory function or project template.

Internal verification

Render and inspect the final files before handoff. Verification is agent-side work, not delivered reproduction code.

Do not place renderer measurements, bounding-box inspection, identifier discovery, PDF or PNG inspection, source audits, directory audits, QA report writers, or verification-result dictionaries in delivered plotting or preprocessing scripts. Use temporary task code or skill-bundled validation tools, write diagnostic artifacts outside the retained set only when necessary, and remove artifacts created by the current task after verification.

Delivered scripts may retain concise checks for missing inputs, required columns, empty data, non-finite plotted values, and scientific invariants needed to interpret the result. Keep all other checks internal.

Before handoff, confirm scientific meaning, labels and units, authorized text, panel identifiers, layout and guide clearance, glyph coverage, output size and resolution, applicable geospatial behavior, and the retained-file allowlist. For journal="nat2", verify internally that the saved PDF is 183 mm wide within 0.2 mm and that PNG dimensions agree with the selected DPI. Use references/verification.md for the detailed procedure and do not retain a verification report.

Optional references

Load only the reference needed for a non-trivial decision:

• references/scientific-principles.md: ambiguous scientific question, preprocessing boundary, or processed-data design.
• references/layout.md: complex topology, fixed-aspect geometry, whitespace, alignment, clipping, or panel-identifier conflicts.
• references/verification.md: detailed internal QA procedures. Never copy its diagnostic implementation into delivered scripts.
• references/geospatial.md: CRS, raster, vector, or GeoAxes details.
• references/api.md: unfamiliar commands or parameter semantics.
• references/color.md: advanced colormap construction or perceptual checks.
• references/recipes.md: a concise starting pattern for a matching figure.

References inform implementation and internal verification. They do not expand the retained task artifact allowlist.