Skip to main content

Utility functions related to the Cash statistic

Project description

.. image:: https://img.shields.io/pypi/v/cashstatistic.svg
:alt: PyPi
:target: https://pypi.python.org/pypi/cashstatistic
.. image:: https://img.shields.io/pypi/l/cashstatistic.svg
:alt: MIT
:target: https://mit-license.org/license.txt
===============
cashstatistic
===============
**Utility functions related to the Cash statistic**


The Poisson distribution is

P(x|mu) = exp(-mu) mu^x / x!

The `Cash statistic <http://adsabs.harvard.edu/abs/1979ApJ...228..939C>`_ is defined to be the model (mu) dependent part of -2ln(P), analogous to the role that chi^2 plays for the Gaussian distribution,

C = 2( mu - x\*ln(mu) ).

A modified version,

C_m = 2( mu - x + x\*ln(x/mu) ),

is equivalent to C for parameter inference (i.e. has the same dependence on mu), and also has the nice property of becoming equivalent to chi^2 when x is large. `Kaastra (2017) <http://adsabs.harvard.edu/abs/2017A%26A...605A..51K>`_ was kind enough to provide approximate expressions for the mean and variance of C_m, which can be used to determine whether the actual C_m corresponding to a fitted model is indicative of a good fit (just as chi^2 does for the Gaussian distribution).

This package contains python code to calculate C, C_m, and the theoretical mean and variance of C_m. The `GitHub repo <https://github.com/abmantz/cstat>`_ contains implementations in other languages.


Project details


Download files

Download the file for your platform. If you're not sure which to choose, learn more about installing packages.

Source Distribution

cashstatistic-0.1.1.tar.gz (4.1 kB view details)

Uploaded Source

Built Distribution

cashstatistic-0.1.1-py2-none-any.whl (4.9 kB view details)

Uploaded Python 2

File details

Details for the file cashstatistic-0.1.1.tar.gz.

File metadata

  • Download URL: cashstatistic-0.1.1.tar.gz
  • Upload date:
  • Size: 4.1 kB
  • Tags: Source
  • Uploaded using Trusted Publishing? No

File hashes

Hashes for cashstatistic-0.1.1.tar.gz
Algorithm Hash digest
SHA256 abf60cd19df94258f964728b95ca083716018b951907fc9c9a64d5c389b59d45
MD5 bacac35dd68f2a162353cc9d4fc2a053
BLAKE2b-256 5c985b758ed894a57bda1f8addc73f36f98af3b9dceeba12a8e65ff2b708bcea

See more details on using hashes here.

File details

Details for the file cashstatistic-0.1.1-py2-none-any.whl.

File metadata

File hashes

Hashes for cashstatistic-0.1.1-py2-none-any.whl
Algorithm Hash digest
SHA256 3b264751f1aab625d1b6320a434f6f7ef793fbb7164d1d07c8e7816aeceae0f0
MD5 6a32202cc09020ed9123242880d1bc77
BLAKE2b-256 037d132c910e4aa3c7460b73d5027a5b2648c379e057b0a7614a861e8c382325

See more details on using hashes here.

Supported by

AWS Cloud computing and Security Sponsor Datadog Monitoring Fastly CDN Google Download Analytics Pingdom Monitoring Sentry Error logging StatusPage Status page