.. _0.15.1_notes:

===========================
SimPEG 0.15.1 Release Notes
===========================

August 27th, 2021

This patch release contains several small bug fixes and improvements to the code base.

Updates
=======
We now have a simple depth weighting function that can be used as cell weights for
inversions. It is based off of the common potential fields definition:

.. code-block:: python

    wz = 1/(z - z_0)**(q/2)

The way SimPEG handles the definition of standard deviation calculated from the mix
of relative error and noise levels is slightly changed to respect a more statistically
accurate combination of the two components. It is now:

.. code-block:: python

    standard_deviation = sqrt(noise_level**2 + (relative_error * abs(d_obs))**2)

In addition,

* Removed a bit of dead code
* Fixed some typos in documentation
* Removed all references to old numpy matrix class and replaced with
  appropriate array functions.
* Added clarification to the gravity examples explaining why SimPEG's gravity module
  looks backwards.
* removed some internal references to deprecated properties


Contributors
============
This is a combination of contributors and reviewers who've made contributions towards
this release (in no particular order).

* `@thast <https://github.com/thast>`__
* `@jcapriot <https://github.com/jcapriot>`__
* `@xiaolongw1223 <https://github.com/xiaolongw1223>`__
* `@lheagy <https://github.com/lheagy>`__
* `@domfournier <https://github.com/domfournier>`__
* `@prisae <https://github.com/prisae>`__

Pull requests
=============

* `#1004 <https://github.com/simpeg/simpeg/pull/1004>`__: Depth weighting function in "model_utils.py"
* `#1009 <https://github.com/simpeg/simpeg/pull/1009>`__: Fix PGI gallery example
* `#1016 <https://github.com/simpeg/simpeg/pull/1016>`__: Remove dead code
* `#1019 <https://github.com/simpeg/simpeg/pull/1019>`__: Update receivers.py
* `#1022 <https://github.com/simpeg/simpeg/pull/1022>`__: Change definition of standard deviation
* `#1024 <https://github.com/simpeg/simpeg/pull/1024>`__: Add notes to gravity examples
* `#1025 <https://github.com/simpeg/simpeg/pull/1025>`__: Updates to fix the test errors
* `#1026 <https://github.com/simpeg/simpeg/pull/1026>`__: Replace np.matlib.repmat by np.tile
* `#1027 <https://github.com/simpeg/simpeg/pull/1027>`__: Replace np.matrix by regular ndarrays
* `#1029 <https://github.com/simpeg/simpeg/pull/1029>`__: Fix Typo in static_utils.py
* `#1034 <https://github.com/simpeg/simpeg/pull/1034>`__: rename .freqs to frequencies
* `#1035 <https://github.com/simpeg/simpeg/pull/1035>`__: 0.15.1 Release Notes