Statistical & informatics codes at the Astrophysics Source Code Library

Posted by Feigelson, Eric at December 06. 2014

The Astrophysics Source Code Library (ASCL) is a repository with ~1000 contributed computer codes, growing ~1/day. While many are intended for analysis of data from specific astronomical instruments or astrophysical calculations, some are broadly applicable codes for advanced data analysis. A selection of these ASCL codes based on public-domain languages are listed here, beginning with recent contributions. They have many capabilities in statistical methods, advanced computational algorithms, applied mathematics, data visualization, and software infrastructure

Additional in these areas are very welcome, both inside and outside the ASCL. ASAIP members may present them in this Software Forum `conversation', or email the information to Eric Feigelson (edf .at. astro.psu.edu) who will make additions to this list.

Last update: December 2014.

NDF: Extensible N-dimensional Data Format Library for storage of N-dimensional arrays based on the Hierarchical Data System
Anmap: Image and data analysis with modeling tools
AMADA: Analysis of Multidimensional Astronomical DAtasets based on hierarchical clustering and PCA
HOPE: Just-in-time Python compiler for astrophysical computation that translations Python code into C++ for numerical optimization
MEPSA: Multiple Excess Peak Search Algorithm for analyzing multimodal behaviors in uniformly sampled time series
DIAMONDS: high-DImensional And multi-MOdal NesteD Sampling' for Bayesian inference with nested sampling Monte Carlo algorithm for multi-modal likelihoods
Slim: Numerical data compression for scientific data sets A rapid C++ code for compression of physics data
PhotoRApToR: PHOTOmetric Research APplication TO Redshifts solves regression and classification problems with machine learning algorithms, emphasis on the galaxy photo-z problem.
APS: Active Parameter Searching finds frequentist confidence limits and Bayesian credible limits on multi-modal high-dimensional parameter spaces using Gaussian Process interpolation.
NumCosmo: Numerical Cosmology A C library to test cosmological models using cosmic microwave background, supernova Ia and large-scale structure information
LightcurveMC: An extensible lightcurve simulation program C++ and R code to generate and analyze time series including periodic & stochastic behaviors, signal injection, periodograms, Gaussian Process regression, peak-finding, etc.
VisiOmatic: Celestial image viewer Web client for IIPImage to visualize and navigate through large science images from remote locations using mouse- and touch-based devices.
Skycorr: Sky emission subtraction for observations without plain sky information fits and subtracts a line+continuum sky spectrum from a source spectrum.
HEAsoft: Unified Release of FTOOLS and XANADU is a long-standing suite of software tools for X-ray astronomy including imaging, spectral and timing analysis. Includes a Web browser interface.
Imfit: A Fast, Flexible Program for Astronomical Image Fitting is designed for modeling galaxies, or other structures, in Gaussian or Poisson images using different minimization algorithms.
AstroML: Machine learning and data mining in astronomy is a library of statistical and machine learning tools built on numpy, scipy, astropy, scikit-learn and matplotlib in Python. Accompanies 2013 textbook by Ivezic et al.
Period04: Statistical analysis of large astronomical time series analyzes periodicities in multivariate time series with gaps. Supports SAMP protocol for the Virtual Observatory.
MATLAB package for astronomy and astrophysics is a collection of >700 MATLAB functions with astronomical datasets for image processing, ds9 control, spectral analysis, optical, catalog searches, celestial projections, time & coordinate conversions, time series analysis, and many other utilities.
The Starfish Diagram: Statistical visualization tool is a histogram-based statistical visualization tool useful for large datasets for which one needs to understand the standing or significance of a single entry.
STARMAN: Stellar photometry and image/table handling reduces data from imaging systems including crowded-field photometry, aperture photometry programs, star finding, CCD reduction, image and table handling.
GAUSSCLUMPS: Gaussian-shaped clumping from a spectral map decomposes a 3-dimensional image into Gaussian-shape clumps.
COCO: Conversion of Celestial Coordinates performs accurate transformations between multiple coordinate systems
FROG: Time-series analysis gives displays and analysis of time series, linked to PERIOD and TOPCAT.
PERIOD: Time-series analysis package includes chi-squared fitting; CLEAN, discrete Fourier power, Lomb-Scargle spectra; phase dispersion minimization and string length periodograms.
ASURV: Astronomical SURVival Statistics provides statistical analysis for left-censored data (upper limits) including the Kaplan-Meier estimator, univariate two-sample tests, bivariate correlation measures, and linear regressions.
PISA: Position Intensity and Shape Analysis localizes and parameterizes objects in a 2-dimensional image using thresholding or modeling techniques.
DATACUBE: A datacube manipulation package is a command-line package for manipulating and visualizing data cubes from integral field spectroscopy and radio astronomy.
AST: World Coordinate Systems in Astronomy provides a comprehensive range of facilities for attaching world coordinate systems to astronomical data for plotting and astrometry.
SpecPro: Astronomical spectra viewer and analyzer is an interactive program for viewing and analyzing 1- and 2-dimensional astronomical spectra and spectral energy distributions.
carma_pack: MCMC sampler for Bayesian inference is for Bayesian inference on continuous time autoregressive moving average models, including time series with irregular sampling.
SOFA: Standards of Fundamental Astronomy is a collection of ~160 programs, in C and Fortran 77, implementing official IAU algorithms for fundamental astronomy including time scales, Earth rotation & precession, and coordinate systems.
GAIA: Graphical Astronomy and Image Analysis Tool is an image and data-cube tool for astronomy including photometry, contouring, source detection, surface photometry, arbitrary region analysis, blink comparison, and more.
KAPPA: Kernel Applications Package comprises ~180 commands for image processing, data visualization, and manipulation, working with Starlink's various specialized packages.
Viewpoints: Fast interactive linked plotting of large multivariate data sets visually explores large high-dimensional multivariate data using linked scatterplots with brushing, outlier removal, and more.
BAOlab: Image processing program has tools including size measurements, generating synthetic images, convolving two images, and fitting a two-dimensional King model.
Inverse Beta: Inverse cumulative density function (CDF) of a Beta distribution is useful, for example, of sampling from the Bayesian prior of exoplanet orbital eccentricities.
GRay: Massive parallel ODE integrator, implemented in CUDA C/C++, is an ordinary differential equation integrator designed to integrate billions of photons in curved spacetime according to Einstein's general theory of relativity.
MLZ: Machine Learning for photo-Z can be used for regression or classification using machine learning algorithms such as Random Forests and Self-Organizing Maps.
libsharp: Library for spherical harmonic transforms has algorithms for conversion between maps on the sphere (with various pixelisations such as HEALPix) and their spherical harmonic coefficients with advanced informatics
athena: Tree code for second-order correlation functions is a 2d-tree code estimating second-order correlation functions from galaxy catalogues with lensing and other effects, written in C and Python.
BAOlab: Baryon Acoustic Oscillations software Uses the 2-point correlation function to generate a model-dependent covariance matrix for BAO detection and parameterization.
PyGFit: Python Galaxy Fitter gives photometry from images with disparate pixel scales and PSF sizes to extract robust spectral energy distributions from crowded images.
UVMULTIFIT: Fitting astronomical radio interferometric data is a library for fitting models directly to visibility data, based on the CASA packages in Python.
CPL: Common Pipeline Library is a set of ISO-C toolkit to create automated astronomical data reduction pipelines including image- and signal-processing functions, handling images, tables, matrices, strings, property lists, etc.
SPLAT: Spectral Analysis Tool is a graphical tool for displaying, comparing, modifying and analyzing astronomical spectra. Analysis facilities include continuum and line fitting, filtering, and wavelet denoising.
Munipack: General astronomical image processing software includes an advanced image processor, astrometric calibration, calibrated photometry, and CCD data reduction.
Kirin: N-body simulation library for GPUs mimics the behavior of the GRAPE hardware for direct N-body and tree calculations, written in CUDA.
PyMidas: Interface from Python to Midas is an interface between Python and MIDAS, the major ESO legacy general purpose data processing system, as well as PyRAF.
PyDrizzle: Python version of Drizzle provides a semi-automated interface to combine misaligned images.
WND-CHARM: Multi-purpose image classifier analyzes morphologies of galaxy mergers with a large set (up to ~2700) of image features, and then classifies them.
BIE: Bayesian Inference Engine is an object-oriented library for Bayesina inference , written in C++.
XAssist: Automatic analysis of X-ray astrophysics data source detection, spatial, temporal and spectral analysis.
SkyNet: Neural network training tool for machine learning in astronomy is a ANN training code for use in regression, classification, density estimation, clustering and dimensionality reduction, written in C, C++ and MPI.
BAMBI: Blind Accelerated Multimodal Bayesian Inference is a Bayesian inference engine that simultaneously performs Bayesian inference using MultiNest and learns the likelihood function usingSkyNet.
YODA: Yet another Object Detection Application performs object detection, photometry and star-galaxy classification on multi-band astronomical images with inhomogeneous background noise, in C++.
SciDB: Open Source DMAS for Scientific Research is a Data Management and Analytics Software System peta-scale data and analytics organized around multidimensional array storage, with interfaces to R, C++ and Python.
AstroAsciiData: ASCII table Python module imports ASCII tables, retaining values and headings, exporting to formate like FITS, Numpy, and LaTeX.
CUPID: Clump Identification and Analysis Package identifies and characterizes clumps of emission within 1-2-3 dimensional arrays including ClumpFind, GaussClumps, FellWalker and Reinhold algorithms.
AIDA: Adaptive Image Deconvolution Algorithm is an implementation and extension of the MISTRAL myopic deconvolution for 2- and 3-dimensional images with excellent edge preservation and photometric precision, in Python.
SPECX: Spectral Line Data Reduction Package is a general purpose line data reduction system for datacubes including continuum fitting, Fourier transforms, and subcube visualization.
AstroImageJ: ImageJ for Astronomy adapts the biomedical ImageJ package to astronomy with FITS formats, WCS coordinates, photometry and other processing.
Spherical: Geometry operations and searches on spherical surfaces provides a mathematical representation of shapes on the celestial sphere, such as sky coverage and footprints.
K3Match: Point matching in 3D space is a C library with Python bindings for fast matching of points in using 3-dimensional binary trees.
Shapelets: Image Modelling A linear combination of 2-dimensional shapelet basis functions can model any image, particularly efficient for images localized in space.
SOPT: Sparse OPTimisation implements the Sparsity Averaging Reweighted Analysis (SARA) algorithm for image compression, in-painting, and other image analysis.
BEHR: Bayesian Estimation of Hardness Ratios estimates the hardness ratios and their uncertainties for Poisson spectra in X-ray and gamma-ray astronomy.
GaussFit: Solving least squares and robust estimation problems is a programming language for estimation of constrained nonlinear models with outlier treatment.
Astropy: Community Python library for astronomy provides a common framework, core package of code, and affiliated packages for astronomy in Python. Packages include PyFITS, PyWCS, vo, and asciitable.
emcee: The MCMC Hammer is a parallelized Python implementation of Goodman & Weare's Affine Invariant Markov chain Monte Carlo (MCMC) Ensemble sampler designed for Bayesian parameter estimation.
Ginga: Flexible FITS viewer is a viewer for astronomical Flexible Image Transport System files supporting zooming and panning, color and intensity mapping, thresholding, and more.
Xmatch: GPU Enhanced Astronomic Catalog Cross-Matching provides fast cross-matching between two astronomic catalogs using GPU clusters.
GaPP: Gaussian Processes in Python reconstructs a continuous function from discrete data without assuming a parameterization of the function, handling individual error bars on the data.
EPICS: Experimental Physics and Industrial Control System creates distributed soft real-time control systems using many computers for scientific instruments such as particle accelerators and telescopes
ICORE: Image Co-addition with Optional Resolution Enhancement co-adds and mosaics images with interpolation and deconvolution.
NIFTY: A versatile Python library for signal inference is a framework based on Numerical Information Field TheorY for algorithms operating on point sets, n-dimensional regular grids, spherical spaces, and more.
DisPerSE: Discrete Persistent Structures Extractor identifies topological features in noisy 2- and 3-dimensional image or point process data, such as peaks, voids, walls and filamentary structures.
ESO-MIDAS: General tools for image processing and data reduction provides numerous tools including stellar and surface photometry, image sharpening and decomposition, statistics, data fitting, and graphics.
Thrust: Productivity-Oriented Library for CUDA is a parallel algorithms library and interface that enhances programmer productivity and portability between GPUs and multicore CPUs.
S2LET: Fast wavelet analysis on the sphere performs exact spherical harmonic transforms on the sphere and supports HEALPix sampling.
Bayesian Blocks: Detecting and characterizing local variability in time series is a time-domain statistical algorithm for characterizing intensity variations (including localized bursts) in event data, irregularly or evenly spaced time series.
JAGS: Just Another Gibbs Sampler analyzes Bayesian hierarchical models using Markov Chain Monte Carlo simulation, related to the BUGS package.
LSD: Large Survey Database framework is a Python framework and DBMS for distributed storage, cross-matching and querying of large survey catalogs (>10^9 rows, >1 TB).
Astrometry.net: Astrometric calibration of images inputs an astronomical image and returns the pointing, scale, and orientation of that image.
APT: Aperture Photometry Tool is a highly capable GUI for exploring photometric qualities of astronomical images using aperture photometry calculations.
BLOBCAT: Software to Catalog Blobs extracts structures from 2-dimensional images using the flood fill algorithm.
VARTOOLS: Light Curve Analysis Program analyzes astronomical time series including detrending, filtering, Lomb-Scargle & Box Least Squares periodograms, signal injection, and more.
APLpy: Astronomical Plotting Library in Python produces publication-quality plots of FITS images using Matplotlib with overlays, contours, coordinates, and more.
Astropysics: Astrophysics utilities for python is a library containing a variety of utilities and algorithms for reducing, analyzing, and visualizing astronomical data.
PyFITS: Python FITS Module provides an interface to FITS formatted files to PyRAF, the Python-based interface to IRAF.
PyRAF: Python alternative for IRAF is a command language for running Image Reduction and Analysis Facility tasks that is based on the Python scripting language.
RegiStax: Alignment, stacking and processing of images is software for alignment/stacking/processing of images with image alignment and multicore processing.
FITS Liberator: Image processing software was developed by ESA/ESO/NASA to process and edit astronomical science data in FITS format to produce stunning images of the universe.
statpl: Goodness-of-fit for power-law distributed data estimates the parameter of power-law (Pareto) distributed data and calculates goodness-of-fit tests for them.
ImageJ: Image processing and analysis in Java, inspired by the biomedical Image code, can display, edit, analyze, process, save and images.
ImageHealth: Quality Assurance for Large FITS Images, based on CFITSIO and Python wrappers, provides a snapshot of the quality of FITS images and their sources.
Fv: Interactive FITS file editor is an easy-to-use graphical program for viewing and editing any FITS format image or table.
Iris: The VAO SED Application is a GUI application to build and analyze wide-band Spectral Energy Distributions, linked to the Virtual Observatory.
Mayavi2: 3D Scientific Data Visualization and Plotting is a general-purpose, 3D scientific visualization package with an interactive GUI, MATLAB-like interface, widgets and plugins.
Eclipse: ESO C Library for an Image Processing Software Environment is a library offering many image processing operations designed for high speed in C on parallel systems.
Funtools: FITS Users Need Tools is a "minimal buy-in" FITS library and utility package for a variety of operating systems.
GGobi: A data visualization system explores high-dimensional data with grand tours, scatterplots with interactive brushing, parallel coordinates plots, and more.
CORA: Emission Line Fitting with Maximum Likelihood is a spectral line fitting tool based on maximum likelihood technique for Poisson data (e.g. X-ray astronomical spectra).
XEphem: Interactive Astronomical Ephemeris is a scientific-grade interactive astronomical ephemeris package with Solar System ephemerides and graphics, written in C.
PyEphem: Astronomical Ephemeris for Python provides scientific-grade astronomical computations for the Python programming language based on XEphem routines.
Dexter: Data Extractor for scanned graphs is a Java applet to manually digitize a scanned plot by marking points and defining the coordinate transformation from the logical to the physical coordinate system.
Aladin: Interactive Sky Atlas allows the user to visualize digitized astronomical images, superimpose catalogued objects, interactively access SIMBAD/Vizier or Virtual Observatory databases.
CRBLASTER: A Parallel-Processing Computational Framework for Embarrassingly-Parallel Image-Analysis Algorithms, written in C and MPI, is designed for high-throughput cosmic ray rejection in CCD images.
MOPEX: MOsaicker and Point source EXtractor is a package for reducing and analyzing imaging data with frame mosaicking, outlier rejection, source detection and photometry.
SITools2: A Framework for Archival Systems provides a configurable data access layer deployed on already existing scientific laboratory databases.
Starbase Data Tables: An ASCII Relational Database for Unix gives convenient ways of storing, editing, filtering, and retrieving data about data.
FITSH: Software Package for Image Processing is a pipeline for astronomical imaging data including co-additions, interpolations, astrometry, source identification, photometry, and more.
AAOGlimpse: Three-dimensional Data Viewer is a display program that shows FITS data as 3D surfaces that can be rotated and viewed from different angles.
Univiewer: Visualisation Program for HEALPix Maps is a visualisation program for HEALPix maps that can rotate and zoom maps on the sphere in 3D, calculate the power spectra, and more.
PySpecKit: Python Spectroscopic Toolkit is a Python-based spectroscopic analysis and reduction toolkit for all wavebands with procedures for line fitting, baseline-subtraction, and graphics.
MultiNest: Efficient and Robust Bayesian Inference calculates the evidence and posterior samples from distributions that may contain multiple modes and degeneracies in high dimensions.
PyModelFit: Model-fitting Framework and GUI Tool provides an object-oriented framework for designing numerical models to fit data, particularly 1D curve-fitting.
EnBiD: Fast Multi-dimensional Density Estimation estimates the densities of data samples in n-dimensions based on a metric-free binary space partitioning tree followed by kernel smoothing.
CULSP: Fast Calculation of the Lomb-Scargle Periodogram Using Graphics Processing Units
WCSTools: Image Astrometry Toolkit is a library of utilities for relating image pixels to sky coordinates in FITS and other formats, and more.
GIPSY: Groningen Image Processing System is a highly interactive software system for the reduction and display of astronomical data at different wavebands.
SkyCat: Visualization and Catalog and Data Access Tool is a tool that combines visualization of images and access to catalogs and archive data for astronomy.
IMCAT: Image and Catalogue Manipulation Software is a collection of stand-alone command-line tools addressing FITS files, image calculations, and catalog tools.
LePHARE: Photometric Analysis for Redshift Estimate computes photometric redshifts and SED fits to galaxy population synthesis models.
Hyperz: Photometric Redshift Code finds the redshift of each object by SED fitting.
BPZ: Bayesian Photometric Redshift Code utilizing prior information such as the redshift distributions or the galaxy morphological type.
AMUSE: Astrophysical Multipurpose Software Environment is a framework for existing astrophysics codes that calculate gravitational dynamics, stellar evolution, hydrodynamics and radiative transport.
CASA: Common Astronomy Software Applications is a broad system to support interferometric and single-dish radio astronomical telescopes, in Python.
Clumpfind: Determining Structure in Molecular Clouds analyzes the clumpy structure in a data cube by searching for peaks in a smoothed image and extending them to lower intensities.
HEALPix: Hierarchical Equal Area isoLatitude Pixelization of a sphere produces a subdivision of a spherical surface with equal-area pixels centered in rings of constant latitude.
PLplot: Cross-platform Software Package for Scientific Plots is C library package for creating scientific plots. with device drivers for non-interactive and interactive plotting.
E3D: The Euro3D Visualization Tool is a package of tools for the analysis and visualization of 3-dimensional Integral Field Spectroscopy data.
MIRIAD: Multi-channel Image Reconstruction, Image Analysis, and Display is a radio interferometry reduction package taking raw visibility data through calibration to the image analysis stage.
Application of Compressive Sampling to Radio Astronomy I: Deconvolution introduces a deconvolution method for point and extended sources in interferometric data.
STILTS: Starlink Tables Infrastructure Library Tool Set processes tabular data in many formats with cross-matching, plotting, calculations, filtering, sorting and Virtual Observatory access.
The DTFE public software: The Delaunay Tessellation Field Estimator code reconstructs fields by tesselation interpolation of discrete measurements in 2- and 3-dimensions.
Ganalyzer: A tool for automatic galaxy image analysis classifies galaxies based on radial intensity and spirality.
GALFIT: Detailed Structural Decomposition of Galaxy Images is a 2-dimensional fitting algorithm designed to extract structural components from galaxy images.
DAOPHOT: Crowded-field Stellar Photometry Package is based on aperture photometry, local sky brightness, and least-squares profile fits.
CHIWEI: A Code of Goodness of Fit Tests for Weighted and Unweighed Histograms
PGPLOT: Device-independent Graphics Package for Simple Scientific Graphs
S2PLOT: Three-dimensional (3D) Plotting Library with dynamic geometry, user control, and 4-dimensional animations
VisIt: Interactive Parallel Visualization and Graphical Analysis Tool generates visualizations of 2- and 3-dimensiona scalar & vector terascale data on structured or unstructured meshes, with animation.
ParaView: Data Analysis and Visualization Application allows interactive visualization of terascale datasets in 3-dimensions.
Cactus: HPC infrastructure and programming tools provides computational scientists with a collaborative, modular and portable programming environment for parallel high performance computing.
HOP: A Group-finding Algorithm for N-body Simulations uses coordinate-free local density gradients and spatially adaptive kernel smoothing to identify groups.
TOPCAT: Tool for OPerations on Catalogues And Tables is an interactive graphical viewer and editor for tabular data for analysis and manipulation of source catalogues and other tables, including links to the Virtual Observatory.
DAME: A Web Oriented Infrastructure for Scientific Data Mining & Exploration is a Web-based, VObs compliant, data mining infrastructure for exploring massive data sets with machine learning methods.
VisIVO: Integrated Tools and Services for Large-Scale Astrophysical Visualization is a suite of tools and services for high-performance, multidimensional visualization of very large-scale astrophysical datasets for the Virtual Observatory.
yt: A Multi-Code Analysis Toolkit for Astrophysical Simulation Data is an open source, community-developed astrophysical analysis and visualization toolkit originally designed for AMR hydrodynamical calculations.
CFITSIO: A FITS File Subroutine Library is a library of C and Fortran subroutines for reading, writing, manipulating and filtering data files in the Flexible Image Transport System format.
fpack: FITS Image Compression Program s a utility program for optimally compressing images in the FITS data format.
Needatool: A Needlet Analysis Tool for Cosmological Data Processing performs data analysis based on needlets, a wavelet rendition powerful for the analysis of fields defined on a sphere.
Libpsht: Algorithms for Efficient Spherical Harmonic Transforms is a collection of algorithms for efficient conversion between spatial-domain and spectral-domain representations of data defined on the sphere.
ADAPTSMOOTH: A Code for the Adaptive Smoothing of Astronomical Images serves to smooth astronomical images in an adaptive fashion in order to enhance the signal-to-noise ratio (S/N).
DNEST: Diffusive Nested Sampling is a general Monte Carlo method based on Nested Sampling (NS) for sampling complex probability distributions and estimating the normalising constant.
DimReduce: Nonlinear Dimensionality Reduction of Very Large Datasets with Locally Linear Embedding (LLE) and its Variants
Extreme Deconvolution: Density Estimation using Gaussian Mixtures in the Presence of Noisy, Heterogeneous and Incomplete Data, treating heteroscedasticity.
Montage: An Astronomical Image Mosaicking Toolkit s an open source code toolkit for assembling Flexible Image Transport System (FITS) images into custom mosaics.
FastChi: A Fast Chi-squared Technique For Period Search of Irregularly Sampled Data is a fast, powerful technique for detecting periodicity.
Parameter Estimation from Time-Series Data with Correlated Errors: A Wavelet-Based Method and its Application to Transit Light Curves where the noise has uncorrelated and 1/f-type autocorrelated components.
SExtractor: Source Extractor optimally detects, de-blends, measures and classifies sources from astronomical images, with a neural network for star-galaxy separation.
SWarp: Resampling and Co-adding FITS Images Together by re-mapping the pixels to a new projection and co-adding them with weights.
partiview: Immersive 4D Interactive Visualization of Large-Scale Simulations of particle data using virtual reality tools.
AstroMD: A Multi Dimensional Visualization and Analysis Toolkit for Astrophysics uses virtual reality techniques to travel through a multi-dimensional data space.
FTOOLS: A general package of software to manipulate FITS files is a modular collection of utilities for processing and analyzing data in the FITS format.
IRAF: Image Reduction and Analysis Facility includes programs for general image processing and graphics, plus many for the reduction and analysis of optical and IR astronomy data.
AIPS: Astronomical Image Processing System is a software package for interactive and batch calibration and editing of astronomical data, typically radio interferometric data.
ISIS: A method for optimal image subtraction based on kernel estimation.
SLOPES: Least-squares linear regression lines for bivariate datasets computs six least-squares lines for unweighted data, four of them treating the variables symmetrically.