cassie_overview/doc_algorithms/statistics.js_Doc.md

+## Module: statistics.js
+### Comprehensive Analysis of `statistics.js`
+
+#### Module Name
+- **Module Name**: `statistics.js`
+
+#### Primary Objectives
+- **Purpose**: This module is designed to calculate and analyze various statistics related to shorelines and transects. It includes functions to compute distances, classify changes, and generate comprehensive statistical summaries.
+
+#### Critical Functions
+1. **`calculateDistances`**:
+   - **Role**: Calculates the distance of each shoreline to a point of interest on a transect.
+   - **Parameters**: `transect`, `baseline`, `shorelines`
+   - **Returns**: `ee.Dictionary` containing distances.
+
+2. **`estevesLabelling`**:
+   - **Role**: Classifies the transect change rate using intervals proposed by Esteves and Finkl (1998).
+   - **Parameters**: `lrr` (linear regression rate)
+   - **Returns**: `ee.String` with the classified label.
+
+3. **`calculateStatistics`**:
+   - **Role**: Computes general DSAS statistics (SCE, NSM, EPR, LRR) and Esteves classification for a transect.
+   - **Parameters**: `measurement` (dictionary of distances)
+   - **Returns**: `ee.Dictionary` with the calculated statistics.
+
+4. **`complementaryProperties`**:
+   - **Role**: Appends useful transect data to its properties.
+   - **Parameters**: `transect`, `measurement`, `keepProps`
+   - **Returns**: `ee.Dictionary` with useful and kept properties.
+
+5. **`generateTransectsStatistics`**:
+   - **Role**: Adds DSAS statistics and Esteves classification to transects.
+   - **Parameters**: `transects`, `baseline`, `shorelines`, `keepProps`
+   - **Returns**: `ee.List<ee.Feature>` with added statistics.
+
+6. **`summaryShorelineStatistics`**:
+   - **Role**: Adds statistics about the distances observed in transects to shorelines.
+   - **Parameters**: `transects`, `shorelines`
+   - **Returns**: `ee.FeatureCollection` with added statistics.
+
+#### Key Variables
+- **`distanceKey`**: Key for distance in the dictionary.
+- **`idKey`**: Key for ID in the dictionary.
+- **`poi`**: Point of interest on the transect.
+- **`distanceTo`**: Function to calculate distance to a coordinate.
+- **`classification`**: Result of Esteves classification.
+- **`distanceList`**: List of distances from the measurement dictionary.
+- **`initialState`**: Initial state for reducing distances.
+- **`stats`**: Reduced statistics dictionary.
+- **`regression`**: List of regression points.
+- **`trend`**: Result of linear regression and correlation.
+- **`summary`**: Summary dictionary for complementary properties.
+- **`shorelineList`**: List of shorelines.
+- **`shorelineTable`**: Dictionary mapping shoreline IDs to features.
+- **`distances`**: Flattened list of distances.
+- **`transformed`**: Dictionary of reduced distances per shoreline.
+
+#### Interdependencies
+- **Interactions with Other Components**:
+  - **`earth-engine`**: Utilizes Earth Engine services for geospatial computations.
+  - **`utils`**: Uses utility functions like `combineReducers` and `serializeList`.
+  - **`metadata`**: Accesses common metadata constants like `TIME_START`, `INTERNALS`, and `ESTEVES_LABELS`.
+  - **`common/utils`**: Uses common utility constants like `EPOCH`.
+
+#### Core vs. Auxiliary Operations
+- **Core Operations**:
+  - Distance calculations (`calculateDistances`)
+  - Statistical computations (`calculateStatistics`)
+  - Classification (`estevesLabelling`)
+  - Generating transect statistics (`generateTransectsStatistics`)
+  - Summarizing shoreline statistics (`summaryShorelineStatistics`)
+
+- **Auxiliary Operations**:
+  - Appending complementary properties (`complementaryProperties`)
+
+#### Operational Sequence
+1. **Distance Calculation**: `calculateDistances` computes distances from shorelines to transects.
+2. **Classification**: `estevesLabelling` classifies the linear regression rate.
+3. **Statistical Computation**: `calculateStatistics` computes various statistics for the transects.
+4. **Property Appending**: `complementaryProperties` appends additional properties to transects.
+5. **Transect Statistics Generation**: `generateTransectsStatistics` integrates all computations and classifications into transects.
+6. **Shoreline Statistics Summary**: `summaryShorelineStatistics` summarizes the statistics for shorelines.
+
+#### Performance Aspects
+- **Performance Considerations**:
+  - Efficient use of Earth Engine's parallel processing capabilities.
+  - Iterative reduction operations for large datasets.
+  - Conditional checks to handle edge cases and empty collections.
+
+#### Reusability
+- **Adaptability for Reuse**:
+  - Functions are modular and can be reused in different contexts involving geospatial analysis.
+  - Parameterized functions allow for flexibility in input data.
+  - Utility functions like `combineReducers` and `serializeList` enhance reusability.
+
+#### Usage
+- **How It Is Used**:
+  - Integrated into a larger geospatial analysis system.
+  - Called by other modules or scripts to compute and append statistical data to geospatial features.
+  - Utilized in workflows involving shoreline and transect analysis.
+
+#### Assumptions
+- **Assumptions Made**:
+  - Input data (transects, shorelines, baseline) are correctly formatted and valid.
+  - Earth Engine services are available and functioning.
+  - Metadata constants (`TIME_START`, `INTERNALS`, `ESTEVES_LABELS`) are correctly defined.
+  - Utility functions (`combineReducers`, `serializeList`) are available and correctly implemented.
+
+This comprehensive analysis provides a detailed understanding of the `statistics.js` module, its functions, and its role within a larger geospatial analysis system.
+## Flow Diagram [via mermaid]
+```mermaid
+graph TD
+    A[calculateDistances] --> B[calculateStatistics]
+    B --> C[estevesLabelling]
+    B --> D[complementaryProperties]
+    D --> E[generateTransectsStatistics]
+    E --> F[summaryShorelineStatistics]
+```
+## Module: statistics.js
+### Comprehensive Analysis of `statistics.js`
+
+#### Module Name
+- **Module Name**: `statistics.js`
+
+#### Primary Objectives
+- **Purpose**: This module is designed to calculate and analyze various statistics related to shorelines and transects. It includes functions to compute distances, classify changes, and generate comprehensive statistical summaries.
+
+#### Critical Functions
+1. **calculateDistances**:
+   - **Role**: Computes the distance of each shoreline to a point of interest on a transect.
+   - **Parameters**: `transect`, `baseline`, `shorelines`
+   - **Returns**: `ee.Dictionary` containing distances.
+
+2. **estevesLabelling**:
+   - **Role**: Classifies the transect change rate using intervals proposed by Esteves and Finkl (1998).
+   - **Parameters**: `lrr` (linear regression rate)
+   - **Returns**: `ee.String` representing the classification.
+
+3. **calculateStatistics**:
+   - **Role**: Calculates general DSAS statistics (SCE, NSM, EPR, LRR) and Esteves classification for a transect.
+   - **Parameters**: `measurement` (dictionary of distances)
+   - **Returns**: `ee.Dictionary` containing the statistics.
+
+4. **complementaryProperties**:
+   - **Role**: Appends useful transect data to its properties.
+   - **Parameters**: `transect`, `measurement`, `keepProps`
+   - **Returns**: `ee.Dictionary` with useful and kept properties.
+
+5. **generateTransectsStatistics**:
+   - **Role**: Adds DSAS statistics and Esteves classification to transects.
+   - **Parameters**: `transects`, `baseline`, `shorelines`, `keepProps`
+   - **Returns**: `ee.List<ee.Feature>` with added statistics.
+
+6. **summaryShorelineStatistics**:
+   - **Role**: Adds statistics about the distances observed in transects to shorelines.
+   - **Parameters**: `transects`, `shorelines`
+   - **Returns**: `ee.FeatureCollection` with added statistics.
+
+#### Key Variables
+- **distanceKey**: Key for distance in the dictionary.
+- **idKey**: Key for ID in the dictionary.
+- **poi**: Point of interest on the transect.
+- **distanceTo**: Function to calculate distance to a coordinate.
+- **classification**: Result of Esteves classification.
+- **distanceList**: List of distances from the measurement dictionary.
+- **initialState**: Initial state for reducing distances.
+- **stats**: Reduced statistics dictionary.
+- **regression**: List of regression points.
+- **trend**: Result of linear regression and correlation.
+- **summary**: Summary dictionary for complementary properties.
+
+#### Interdependencies
+- **Interactions with Other Components**:
+  - **Earth Engine (ee)**: Utilizes Google Earth Engine for geospatial computations.
+  - **Common Metadata**: Imports constants like `TIME_START`, `INTERNALS`, `ESTEVES_LABELS`.
+  - **Utilities**: Uses utility functions like `combineReducers`, `serializeList`.
+
+#### Core vs. Auxiliary Operations
+- **Core Operations**:
+  - Distance calculation (`calculateDistances`)
+  - Statistical analysis (`calculateStatistics`)
+  - Classification (`estevesLabelling`)
+  - Generating transect statistics (`generateTransectsStatistics`)
+  - Summarizing shoreline statistics (`summaryShorelineStatistics`)
+
+- **Auxiliary Operations**:
+  - Appending properties (`complementaryProperties`)
+  - Utility functions for combining reducers and serializing lists.
+
+#### Operational Sequence
+1. **Distance Calculation**: `calculateDistances` computes distances from shorelines to transects.
+2. **Statistical Analysis**: `calculateStatistics` processes these distances to generate DSAS statistics.
+3. **Classification**: `estevesLabelling` classifies the transect change rate.
+4. **Property Appending**: `complementaryProperties` adds useful properties to transects.
+5. **Transect Statistics Generation**: `generateTransectsStatistics` integrates all previous steps to enrich transects with statistics.
+6. **Shoreline Statistics Summary**: `summaryShorelineStatistics` aggregates and summarizes statistics for shorelines.
+
+#### Performance Aspects
+- **Considerations**:
+  - **Efficiency**: Uses Earth Engine's efficient geospatial computation capabilities.
+  - **Scalability**: Designed to handle large datasets typical in geospatial analysis.
+  - **Optimization**: Utilizes reducers and efficient data structures to minimize computation time.
+
+#### Reusability
+- **Adaptability**:
+  - Functions are modular and can be reused in different contexts involving geospatial analysis.
+  - Utility functions like `combineReducers` and `serializeList` enhance reusability.
+
+#### Usage
+- **How It Is Used**:
+  - Integrated into larger geospatial analysis workflows.
+  - Called by other modules or scripts to compute and analyze shoreline and transect statistics.
+  - Utilized in environmental monitoring, coastal management, and research projects.
+
+#### Assumptions
+- **Assumptions Made**:
+  - Input data (transects, shorelines, baseline) are correctly formatted and valid.
+  - Earth Engine environment is properly set up and accessible.
+  - Constants and utility functions are correctly imported and available.
+  - Dates and distances are meaningful and within expected ranges for the analysis.
+
+This comprehensive analysis provides a detailed understanding of the `statistics.js` module, its functions, and its role within a larger geospatial analysis system.
+## Flow Diagram [via mermaid]
+```mermaid
+graph TD
+    A[User] -->|provides transects, baseline, shorelines| B[generateTransectsStatistics]
+    B -->|calls| C[calculateDistances]
+    B -->|calls| D[calculateStatistics]
+    B -->|calls| E[complementaryProperties]
+    B -->|returns transects with added statistics| F[User]
+    G[User] -->|provides transects, shorelines| H[summaryShorelineStatistics]
+    H -->|returns shorelines with added statistics| I[User]
+```