Expresso

Tools to compress and express information from maps of the sky

Expresso is a Python package designed for processing, compressing, and analyzing astronomical sky maps, with a particular focus on cosmic microwave background (CMB) data and other cosmological observations.

Features

• Sky Map Processing: Load, manipulate, and analyze astronomical sky maps
• Data Compression: Advanced compression algorithms optimized for astronomical data
• Multiple Formats: Support for FITS, HEALPix, and other standard astronomical formats
• Coordinate Systems: Handle different coordinate systems (galactic, equatorial, ecliptic)
• Command Line Interface: Easy-to-use CLI tools for common operations
• Extensible: Modular design for easy extension and customization

Installation

From PyPI (when available)

pip install expresso

From Source

git clone https://github.com/CMBAgents/expresso.git
cd expresso
pip install -e .

Dependencies

Core dependencies:

• numpy >= 1.20.0
• scipy >= 1.7.0
• astropy >= 5.0.0 (for FITS I/O)
• healpy >= 1.15.0 (for HEALPix support)

Development dependencies:

• pytest >= 6.0.0 (for testing)
• black >= 22.0.0 (for code formatting)
• mypy >= 0.950 (for type checking)

Quick Start

Basic Usage

import expresso

# Create a random sky map for testing
skymap = expresso.create_random_skymap(nside=64, seed=42)

# Get basic statistics
stats = skymap.get_stats()
print(f"Mean: {stats['mean']:.3e}, Std: {stats['std']:.3e}")

# Compress the sky map
compressed_data = expresso.compress_skymap(
    skymap.data, 
    method="wavelet", 
    compression_ratio=0.1
)

# Get compression info
info = expresso.get_compression_info(compressed_data)
print(f"Space saved: {info['space_saved_percent']:.1f}%")

# Decompress
decompressed_data = expresso.decompress_skymap(compressed_data)

Loading and Saving Sky Maps

# Load a sky map from FITS file
skymap = expresso.load_skymap("data/skymap.fits")

# Process the sky map
smoothed = skymap.smooth(fwhm=5.0)  # 5 arcmin FWHM
downgraded = skymap.downgrade(factor=2)

# Save processed sky map
expresso.save_skymap(smoothed, "output/smoothed_map.fits")

Command Line Interface

# Compress a sky map
expresso compress input.fits output.compressed --method wavelet --ratio 0.1

# Get information about a compressed file
expresso info output.compressed

# Generate a random sky map for testing
expresso generate test_map.fits --nside 128 --seed 42

# Get statistics about a sky map
expresso stats input.fits

Package Structure

expresso/
├── __init__.py          # Main package interface
├── compression.py       # Data compression algorithms
├── skymap.py           # Sky map processing and manipulation
├── io.py               # Input/output operations
├── utils.py            # Utility functions and helpers
├── config.py           # Configuration management
├── cli.py              # Command-line interface
├── tests/              # Test suite
│   └── test_*.py
└── examples/           # Usage examples
    └── basic_usage.py

Modules

expresso.compression

Advanced compression algorithms for astronomical data:

• Wavelet-based compression
• Principal Component Analysis (PCA)
• Singular Value Decomposition (SVD)
• Configurable compression ratios and quality settings

expresso.skymap

Sky map processing and manipulation:

• SkyMap class for representing astronomical sky maps
• Coordinate system transformations
• Statistical analysis and masking
• Smoothing and resolution changes

expresso.io

Input/output operations for various formats:

• FITS file support via astropy
• HEALPix format support via healpy
• NumPy array formats
• Metadata preservation

expresso.utils

Utility functions for astronomical calculations:

• Angular distance calculations
• Coordinate transformations
• Unit conversions
• Beam functions and physical constants

expresso.config

Configuration management:

• Default settings and parameter validation
• User configuration files
• Runtime configuration updates

Examples

See the examples/ directory for detailed usage examples:

• basic_usage.py: Comprehensive example showing core functionality
• More examples coming soon!

Development

Running Tests

# Install development dependencies
pip install -e ".[dev]"

# Run tests
pytest

# Run tests with coverage
pytest --cov=expresso

Code Style

This project uses black for code formatting and mypy for type checking:

# Format code
black expresso/

# Type checking
mypy expresso/

Contributing

Contributions are welcome! Please see the contributing guidelines for details.

License

This project is licensed under the MIT License - see the LICENSE file for details.

Acknowledgments

• Built for the cosmic microwave background (CMB) and cosmology community
• Designed to work with standard astronomical data formats and tools
• Inspired by the need for efficient storage and transmission of large sky maps

Support

• Documentation: GitHub README
• Issues: GitHub Issues
• Discussions: GitHub Discussions