- Extract carrier names from MultiIndex in stochastic networks
- Automatically replicate new carriers across all scenarios
- Preserve MultiIndex structure when concatenating carriers
- Add comprehensive unit tests for stochastic network support
- Update stochastic_network() example to set carriers and call add_missing_carriers()

Detect stochastic scenarios and adjust plotting behavior to ensure seaborn
automatically aggregates scenarios with error bars. Collection indices are
used for faceting instead of color when scenarios are present. This maintains
error bar functionality while supporting NetworkCollection plotting.

Stochastic networks now display error bars in plotly interactive bar plots.
Scenarios are automatically aggregated (mean) and standard deviations are
shown as error bars. Detection ensures only true stochastic networks are
aggregated, not collections with indices named 'scenario'.

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Co-Authored-By: Claude <[email protected]>

- Use self.n_save.components for safer component iteration
- Change logger level from info to debug for no missing carriers
- Move generate_colors to common.py as standalone function
- Update tests to use common.generate_colors
- Simplify _get_investment_periods to use n.periods directly
- Use n._index_names directly (available on both Networks and Collections)

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Co-Authored-By: Claude <[email protected]>

Addresses review comment #10 (lkstrp at plotter.py:759) about reducing boilerplate
in statistics plotting code. This change consolidates ~110 lines of duplicated logic
between StatisticPlotter and StatisticInteractivePlotter.

Changes:
- Created _StatisticPlotterBase base class with shared _prepare_chart_data() method
- Both StatisticPlotter and StatisticInteractivePlotter now inherit from this base
- Moved common logic for parameter validation, schema application, and data
  preparation into the base class method
- Fixed _get_investment_periods() to handle NetworkCollection gracefully by
  catching NotImplementedError when accessing the periods attribute

Benefits:
- Reduces code duplication and maintenance burden
- Ensures consistency between static and interactive plotters
- Makes future changes easier to implement in one place
- Improves code readability

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Co-Authored-By: Claude <[email protected]>

Add unique_carriers as a property on the Components base class, following
the established pattern for component-related properties like ports.

Changes:
- Added unique_carriers property to pypsa.components.components.Components
- API: `n.c.<component>.unique_carriers` (e.g., `n.c.generators.unique_carriers`)
- Updated carriers.py to iterate over all components and collect unique carriers
- Updated release notes to document the new API location

Benefits:
- Follows consistent API pattern similar to ports property
- Each component can report its own unique carriers
- More modular and intuitive API design

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Co-Authored-By: Claude <[email protected]>

Refactor get_carrier_colors and get_carrier_labels to reduce code duplication
by extracting common logic into a helper method _get_carrier_attribute.

Changes:
- Added _get_carrier_attribute() helper method to extract carrier attributes
  with optional nice name mapping
- Simplified get_carrier_colors() to use the helper method
- Simplified get_carrier_labels() with clearer logic
- Added comprehensive docstrings to all methods
- Added explanatory comments for stochastic network handling

Benefits:
- Reduces code duplication (~15 lines)
- Makes the code more maintainable and easier to extend
- Provides a pattern that could be generalized for other component attributes
- Clearer separation of concerns

The helper method could potentially be extended in the future to work with
other component types beyond carriers, making it a foundation for more
general component attribute access patterns.

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Co-Authored-By: Claude <[email protected]>

Add a `unique` property to the Carriers class that handles extracting unique
carrier names from both regular and stochastic networks. This eliminates
repeated conditional logic throughout the codebase.

Changes:
- Added `unique` property to pypsa.components._types.carriers.Carriers
- Returns unique carrier names, handling MultiIndex for stochastic networks
- Updated assign_colors() to use self.unique (2 usages simplified)
- Updated add_missing_carriers() to use self.unique (1 usage simplified)

Benefits:
- Eliminates 3 instances of if/else blocks checking for scenarios
- Makes code more readable and maintainable
- Provides a single source of truth for accessing unique carrier names
- Reduces coupling to internal index structure

Example usage:
>>> n.c.carriers.unique
Index(['AC', 'gas', 'solar', 'wind'], dtype='object', name='name')

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Co-Authored-By: Claude <[email protected]>

- Add timestep-to-snapshot mapping for multi-period networks in area/line plots
- Fix artificial trace generation for stacked area plots with proper array dimensions
- Extend filtered columns to include scenario and period for proper grouping
- Add auto-faceting for multi-period, stochastic, and collection networks

- Add missing `import pypsa` statements to doctest examples
- Mark illustrative examples with `# doctest: +SKIP` where appropriate
- Add `# doctest: +NORMALIZE_WHITESPACE` to handle pandas DataFrame formatting
- Update expected output in add_missing_carriers examples to include 'AC' carrier

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Co-Authored-By: Claude <[email protected]>

Add tests for previously untested functionality to improve code coverage:

- Test assign_colors method with various scenarios:
  - Basic color assignment
  - Specific carrier selection
  - Different color palettes
  - Overwrite behavior
  - Stochastic networks

- Test unique_carriers property:
  - Empty components
  - Components with and without carrier attribute
  - Filtering empty strings and NaN values

- Test has_scenarios property for NetworkCollection:
  - Collections without scenarios
  - Collections with mixed networks
  - Collections with only stochastic networks

- Test error handling for conflicting arguments in add_missing_carriers

All 32 tests pass successfully.

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Co-Authored-By: Claude <[email protected]>

Add tests to achieve 100% coverage on pypsa/components/_types/carriers.py:

- Test assign_colors with single string carrier name (covers line 127)
- Test add_missing_carriers on stochastic network without palette
  (covers branch 295->300 with palette=None case)

All 33 carrier tests pass. Carriers module now has 100% line and branch coverage.

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Co-Authored-By: Claude <[email protected]>

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