Sncosmo

===================

- Add Hounsell et al. (2017) SALT2 model to built-ins.

- Add ``remote_timeout`` configuration option.

- Build system: remove build-time dependency on astropy helpers.

- Bugfixes:

- Correctly delete empty files created when a download fails.

- Use pseudo-inverse when inverting covariance matrix for increased stability.

- Fix an issue with pickling on Cython 0.26+.

- Fixed problem where ``data['fluxcov']`` was unintentionally being modified
in-place when passed to ``fit_lc``.

- Fixed problem where ``'fluxcov'`` not recognized as a valid name for
covariance column in data in ``fit_lc``.

===================

This is a major new release. The highlight is really close compatibility of
the SALT2 model and fitting procedure with ``snfit``, the "official" SALT2
fitter.

- ``SALT2Source``: Internal interpolation scheme of ``SALT2Source``
updated to match ``snfit`` implementation exactly. Test suite now tests
against ``snfit`` implementation.

- ``fit_lc()``:

- Handling of model covariance updated to match that of ``snfit``: model
covariance is fixed for each fit and fit is repeated until convergence.

- New arguments ``phase_range`` and ``wave_range``. If given,
data outside this range will be discarded after an initial fit and
additional fits will be performed until convergence.
With ``phase_range=(-15., 45.)`` and ``wave_range=(3000., 7000.)``,
behavior approximates that of snfit with default arguments.

- Added support for covariance in photometric data measurements, and
this covariance is used in ``fit_lc()`` if present. Covariance
is stored as a ``'fluxcov'`` column in the table of measurements.

- Result includes two new attributes: ``data_mask``, a boolean array
indicating which rows in the input data were used in the final fit
(since multiple fits might be performed), and ``nfit``, the number
of fits performed.

- New argument ``warn`` can be set to False to turn off warnings about
dropping bands outside model wavelength range.

- ``read_lc()``:

- Added support for reading snfit-format "covmat" files into
a table of photometry::

>>> data = read_lc('filename', format='salt2', read_covmat=True)
>>> data['Fluxcov'].shape == (len(data), len(data))
True

- New keyword argument ``expand_bands``. When True, the returned band
column will contain ``Bandpass`` objects instead of strings. (Strings
converted to bandpass objects using ``sncosmo.get_bandpass()``.) This
is particularly useful for position-dependent bandpasses in the salt2
file format, such as ``megacampsf``: ``read_lc()`` reads the position from
the header and feeds the position to ``get_bandpass()`` to get a Bandpass
object for the correct position.

- Built-in bandpasses and magnitude systems: Many new built-in bandpasses
and magnitude systems.

- Configuration: The environment variable ``SNCOSMO_DATA_DIR`` can be
used to set the path to the data directory. If set, it takes
precedence over the ``data_dir`` variable in the configuration file
(``$HOME/.astropy/config/sncosmo.cfg``).

===================

- ``SFD98Map`` and ``get_ebv_from_map`` deprecated in favor of separate package
`sfdmap <http://github.com/kbarbary/sfdmap>`_ which has vastly improved
performance (200x faster) for the typical case of scalar coordinates in
ICRS frame.

- ``animate_source()`` deprecated. This is a "fun extra" that is difficult
to test and no longer seems to work.

- Cython implementation of extinction functions has been factored out into
a separate Python module called ``extinction``, which is now a dependency.

- ``Model.bandflux()`` and ``Source.bandflux()`` now integrate on a
fixed wavelength grid of 5 angstroms regardless of the wavelength
grid of the bandpass. This will result in small differences in
results from previous sncosmo versions.

- The internal (publicly undocumented) ``Spectrum`` class now acts
more like ``Model``; in particular, its ``bandflux()`` method now
behaves the same way. As ``Spectrum`` backs ``SpectralMagSystem``,
this makes the integration of models and zeropoint spectra more
consistent.

- Experimental (non-public) support for aliases for bandpasses,
such as ``'SDSS::g'`` for ``'sdssg'``.

- Sources now use cubic rather than quadratic spline interpolation internally.

- ``Model.source_peakmag()`` and ``Model.set_source_peakmag()`` added
as convenience functions for ``Model.source.peakmag()`` and
``Model.source.set_peakmag()`` respectively.

- **[Bugfix]** Fixed missing import of ``math`` module in ``mcmc_lc()``
when using the ``priors`` keyword. [Backported to v1.3.1]
[`143 <https://github.com/sncosmo/sncosmo/issues/143>`_]

===================

This is mostly a bugfix release, but it also **drops support for Python 2.6.**
Python 2.7 is now the minimum supported Python version.

- Updates for compatibility with AstroPy 1.2.

- The registry now handles subclasses more robustly. For example,
if ``magsys`` is an instance of ``SpectralMagSystem``, the following
used to fail::

sncosmo.register(magsys, 'name')
sncosmo.get_magsystem('name')

Now this works. [`132 <https://github.com/sncosmo/sncosmo/issues/132>`_]

- **[Bugfix]** ``SALT2Source`` had a bug under Python 3 (only)
yielding drastically wrong fluxes. Python 2 was not affected. [`138
<https://github.com/sncosmo/sncosmo/issues/138>`_]

===================

- **[API change]** Registry functions moved to the top-level namespace, as
follows:

- ``sncosmo.registry.register()`` -> ``sncosmo.register()``
- ``sncosmo.registry.register_loader()`` -> ``sncosmo.register_loader()``
- ``sncosmo.registry.retrieve()`` -> deprecated, use class-specific
functions such as ``sncosmo.get_bandpass()``.

The old import paths will still work for backwards compatibility.

- ``nest_lc()`` now uses the ``nestle`` module under the hood. A new
keyword ``method`` is available which selects different sampling
methods implemented by ``nestle``. The new methods provide potential
efficiency gains.

- The MLCS2k2 model is now available as a built-in Source, with the
name ``'mlcs2k2'``.

- Bandpasses from the Carnegie Supernova Project added to built-ins.

- In ``realize_lcs()``, a new ``scatter`` keyword makes adding noise
optional.

- **[Bugfix]** Fix built-in Bessell bandpass definitions, which were
wrong by a term proportional to inverse wavelength. This was due to
misinterpretation of the trasmission units. [backported to v1.1.1]
[`111 <https://github.com/sncosmo/sncosmo/issues/111>`_]

===================

This is a mostly bugfix release with more solid support for Python 3.

- Added ``Model.color()`` method.

- Remove ``loglmax`` from result of ``nest_lc()``, which was not
officially documented or supported. Use ``np.max(res.logl)`` instead.

- Fixed bug that caused non-reproducible behavior in
``nest_lc()`` even when ``numpy.random.seed()`` was called
directly beforehand.
[`102 <https://github.com/sncosmo/sncosmo/issues/102>`_]

- Fixed file I/O problems on Python 3 related to string encoding.
[`83 <https://github.com/sncosmo/sncosmo/issues/83>`_,
`85 <https://github.com/sncosmo/sncosmo/issues/85>`_]

- Fixed problem with SDSS bandpasses being stored as integers internally,
preventing them from being used with models with dust.
[`100 <https://github.com/sncosmo/sncosmo/issues/100>`_,
`101 <https://github.com/sncosmo/sncosmo/issues/101>`_]

- Fixed problem where built-in source name and version strings were being
dropped. [`82 <https://github.com/sncosmo/sncosmo/issues/82>`_]

- Minor doc fixes.