Improved CHANGELOG readibility

Author: FBumann

CHANGELOG.md

@@ -2,117 +2,129 @@
 
 All notable changes to this project will be documented in this file.
 
-The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/) and [gitmoji](https://gitmoji.dev)
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
 
-### Fixed
-* Fixed formating issues in the yaml model documentation (line breaks)
-
-### Breaking Changes:
-* Removed `kind` in favor of `style` in plotting functions.
-* Renamed `TimeSeries.active_data` to `TimeSeries.selected_data`
-* `CalculationResults.flow_system` now returns the restorded FlowSystem instead of the `xr.Dataset`. The data can be found under `flow_system_data`.
+### 🚨 Breaking Changes
+* **🚨 BREAKING**: Removed `kind` in favor of `style` in plotting functions
+* **🚨 BREAKING**: Renamed `TimeSeries.active_data` to `TimeSeries.selected_data`
+* **🚨 BREAKING**: `CalculationResults.flow_system` now returns the restored FlowSystem instead of the `xr.Dataset`. The data can be found under `flow_system_data`
 
 ### Added
-* **Scenarios:**
-  * Scenarios can now be used to model uncertainties in the flow system, such as:
-  * Scenarios are passed to a `FlowSystem`. The total objective effect of each scenario is multiplied by a `scenario_weight`. This forms the objective of the optimization.
-* **`CalculationResults`:** 
-  * New dedicated `FlowResults`. 
-  * Dedicated xr.DataArrays for all **flow_rates**, **flow_hours**, and **sizes** of flows are availlable.
-  * Use `effects_per_component()` to retrieve all effects results for every Component. This includes indirect effects that hove their origin in an element, but are inflicted by another effect (ElementA --> CO2 --> Costs))
-* Balanced storage - Storage charging and discharging sizes can now be forced to be equal when optimizing their size by choosing `balanced=True`.
-* Plotting styles can now be changed for all plots. (stacked_bar, line, area)
-* Added plotting style `grouped_bar`
-* Support for pandas.Series and pandas.DataFrame when setting parameters of Elements (internally converted to xarray.DataArrays)
+#### Major Features
+* **Scenarios**: Model uncertainties or **Multi-Period Transformations**
+  * Scenarios are passed to a `FlowSystem` with `scenario_weight` multipliers
+  * Total objective effect of each scenario forms the optimization objective
+  * Sizes might be optimized for each scenario separately, globally or only for a subset of all scenarios (See `InvestmentParameters`).
+* **Balanced Storage**: Storage charging and discharging sizes can now be forced to be equal when optimizing by choosing `balanced=True`
+
+#### Results & Analysis
+* **New dedicated `FlowResults` class
+  * Dedicated xr.DataArrays combining all **flow_rates**, **flow_hours**, or **sizes** of flows
+  * Use `effects_per_component()` to retrieve all effects results for every Component, including indirect effects (ElementA → CO2 → Costs)
+
+#### API Improvements
+* Support for pandas.Series and pandas.DataFrame when setting Element parameters (internally converted to xarray.DataArrays)
+* Improved internal datatypes for clearer data format requirements:
+  * `Scalar` for scalar values only
+  * `TimestepData` for time-indexed data (with optional scenario dimension)
+  * `ScenarioData` for scenario-dimensional data
+
+#### Plotting & Visualization
+* All plotting styles available for both plotly and matplotlib plots: `stacked_bar`, `line`, `area`
+* Added `grouped_bar` plotting style
+* Changed default legend location in plots (now on the right side)
+
+### Deprecated
+* `Calculation.active_timesteps` → Use `Calculation.selected_timesteps` instead
+* ⚠️ Loading Results from prior versions will raise warnings due to FlowResults incompatibility. Some new features cannot be used.
 
-### Changed
-* Improved internal Datatypes to make needed data format more obvious: `Scalar` for only scalar values, `TimestepData` for time-indexed data (which might have a scenario dimension), `ScenarioData` for data with a scenario dimension.
-* `InvestmentParameters` now have a `investment_scenarios` parameter to define which scenarios to define how to optimize the size across scenarios
-* Changed legend location in plots
-
-### Deprecations
-* Renamed `Calculation.active_timesteps` to `Calculation.selected_timesteps`
-* A warning is raised if Results prior ti this version are loaded, as this prevents the FLowResults from being created.
+### Fixed
+* Fixed formatting issues in YAML model documentation (line breaks)
 
 ### Known Issues
 * Scenarios are not yet supported in `AggregatedCalculation` and `SegmentedCalculation`
 
-### Development
-* Greatly improved testing by directly asserting for the correctness of the created equations and variables (and their bounds).
-
 ## [2.1.2] - 2025-06-14
 
 ### Fixed
-- Storage losses per hour where not calculated correctly, as mentioned by @brokenwings01. This might have lead to issues with modeling large losses and long timesteps. 
-  - Old implementation:     $c(\text{t}_{i}) \cdot (1-\dot{\text{c}}_\text{rel,loss}(\text{t}_i)) \cdot \Delta \text{t}_{i}$
-  - Correct implementation: $c(\text{t}_{i}) \cdot (1-\dot{\text{c}}_\text{rel,loss}(\text{t}_i)) ^{\Delta \text{t}_{i}}$
+* **🐛 Critical Fix**: Storage losses per hour calculation corrected (thanks @brokenwings01)
+  * **Impact**: Affects modeling of large losses and long timesteps
+  * **Old**: `c(t_i) · (1-ċ_rel,loss(t_i)) · Δt_i`
+  * **Correct**: `c(t_i) · (1-ċ_rel,loss(t_i))^Δt_i`
 
-### Known issues
-- Just to mention: Plotly >= 6 may raise errors if "nbformat" is not installed. We pinned plotly to <6, but this may be fixed in the future.
+### Known Issues
+* Plotly >= 6 may raise errors if "nbformat" is not installed (pinned to <6 for now)
 
 ## [2.1.1] - 2025-05-08
 
 ### Fixed
-- Fixed bug in the `_ElementResults.constraints` not returning the constraints but rather the variables
+* Fixed `_ElementResults.constraints` returning variables instead of constraints
 
 ### Changed
-- Improved docstring and tests
+* Improved docstrings and tests
 
 ## [2.1.0] - 2025-04-11
 
+### 🚨 Breaking Changes
+* **🚨 BREAKING**: Restructured On/Off state modeling for Flows and Components
+  * Variable renaming: `...|consecutive_on_hours` → `...|ConsecutiveOn|hours`
+  * Variable renaming: `...|consecutive_off_hours` → `...|ConsecutiveOff|hours`
+  * Constraint renaming: `...|consecutive_on_hours_con1` → `...|ConsecutiveOn|con1`
+  * Similar pattern applied to all consecutive on/off constraints
+
 ### Added
-- Python 3.13 support added
-- Logger warning if relative_minimum is used without on_off_parameters in Flow
-- Greatly improved internal testing infrastructure by leveraging linopy's testing framework
+* **Python 3.13 support**
+* Enhanced testing infrastructure leveraging linopy's testing framework
+* Logger warnings for `relative_minimum` usage without `on_off_parameters` in Flow
 
 ### Fixed
-- Fixed the lower bound of `flow_rate` when using optional investments without OnOffParameters
-- Fixed bug that prevented divest effects from working
-- Added lower bounds of 0 to two unbounded vars (numerical improvement)
-
-### Changed
-- **BREAKING**: Restructured the modeling of the On/Off state of Flows or Components
-  - Variable renaming: `...|consecutive_on_hours` → `...|ConsecutiveOn|hours`
-  - Variable renaming: `...|consecutive_off_hours` → `...|ConsecutiveOff|hours`
-  - Constraint renaming: `...|consecutive_on_hours_con1` → `...|ConsecutiveOn|con1`
-  - Similar pattern for all consecutive on/off constraints
+* Fixed `flow_rate` lower bound issues with optional investments without OnOffParameters
+* Fixed divest effects functionality
+* Added missing lower bounds of 0 to unbounded variables (numerical stability improvement)
 
 ## [2.0.1] - 2025-04-10
 
-### Added
-- Logger warning if relative_minimum is used without on_off_parameters in Flow
-
 ### Fixed
-- Replace "|" with "__" in filenames when saving figures (Windows compatibility)
-- Fixed bug that prevented the load factor from working without InvestmentParameters
+* **Windows Compatibility**: Replace "|" with "__" in figure filenames
+* Fixed load factor functionality without InvestmentParameters
+
+### Added
+* Logger warning for `relative_minimum` usage without `on_off_parameters` in Flow
 
 ## [2.0.0] - 2025-03-29
 
-### Changed
-- **BREAKING**: Complete migration from Pyomo to Linopy optimization framework
-- **BREAKING**: Redesigned data handling to rely on xarray.Dataset throughout the package
-- **BREAKING**: Framework renamed from flixOpt to flixopt (`import flixopt as fx`)
-- **BREAKING**: Results handling completely redesigned with new `CalculationResults` class
+### 🚨 Breaking Changes
+* **🚨 BREAKING**: Complete migration from Pyomo to Linopy optimization framework
+* **🚨 BREAKING**: Redesigned data handling using xarray.Dataset throughout
+* **🚨 BREAKING**: Framework renamed from flixOpt to flixopt (`import flixopt as fx`)
+* **🚨 BREAKING**: Complete redesign of Results handling with new `CalculationResults` class
+* **🚨 BREAKING**: Removed Pyomo dependency
+* **🚨 BREAKING**: Removed Period concepts (simplified to timesteps)
 
 ### Added
-- Full model serialization support - save and restore unsolved Models
-- Enhanced model documentation with YAML export containing human-readable mathematical formulations
-- Extend flixopt models with native linopy language support
-- Full Model Export/Import capabilities via linopy.Model
-- Unified solution exploration through `Calculation.results` attribute
-- Compression support for result files
-- `to_netcdf/from_netcdf` methods for FlowSystem and core components
-- xarray integration for TimeSeries with improved datatypes support
-- Google Style Docstrings throughout the codebase
+#### Major Features
+* **Full model serialization**: Save and restore unsolved Models
+* **Enhanced model documentation**: YAML export with human-readable mathematical formulations
+* **Native linopy integration**: Extend flixopt models with linopy language support
+* **Model Export/Import**: Full capabilities via linopy.Model
+
+#### Results & Analysis
+* **Unified solution exploration** through `Calculation.results` attribute
+* **Compression support** for result files
+* **xarray integration** for TimeSeries with improved datatypes support
+
+#### API Improvements
+* `to_netcdf/from_netcdf` methods for FlowSystem and core components
+* Google Style Docstrings throughout codebase
 
 ### Fixed
-- Improved infeasible model detection and reporting
-- Enhanced time series management and serialization
-- Reduced file size through improved compression
+* **Improved infeasible model detection and reporting**
+* Enhanced time series management and serialization
+* Reduced file sizes through better compression
 
 ### Removed
-- **BREAKING**: Pyomo dependency (replaced by linopy)
-- Period concepts in time management (simplified to timesteps)
+- **🚨 BREAKING**: Pyomo dependency (replaced by linopy)
+- **🚨 BREAKING**: Period concepts in time management (simplified to timesteps)