This is a pre-production deployment of Warehouse, however changes made here WILL affect the production instance of PyPI.
Latest Version Dependencies status unknown Test status unknown Test coverage unknown
Project Description

Track the median of a stream of values “on-line” in reasonably efficient fashion.


from mediantracker import MedianTracker
tracker = MedianTracker()
assert tracker.lower_median() == 2
assert tracker.upper_median() == 3

MedianTracker supports efficient median queries on and dynamic additions to a list of values. It provides both the lower and upper median of all values seen so far. Any __cmp__()-able object can be tracked, in addition to numeric types. add() takes log(n) time for a tracker with n items; lower_median() and upper_median() run in constant time. Since all values must be stored, memory usage is proportional to the number of values added (O(n)).

The values can be accessed via iteration over the MedianTracker, though they are not ordered in any particular way:

sum = 0.0
for val in tracker:
    sum += val
mean = sum / len(tracker)

Use this module if you are processing values “on-line,” one at a time, as they arrive, and need to know the new median after each new value (or batch of values). If you just want the median of a whole list, there are much more efficient linear-time median (or more general k-th smallest selection) algorithms. Using this module will take O(nlogn) time and an extra O(n) space to compute the median of n items. On the other hand, a MedianTracker will only take O(nlogn + m) time for any sequence of n adds and m median queries, whereas running a traditional non-incremental median algorithm m times would take O(n*m).

Finally, some sources define the median of an even-length list to be the average of the middle two values. This is easily and efficiently computed (in constant time):

tracker = MedianTracker([1, 2, 3, 4])
median = (tracker.lower_median() + tracker.upper_median()) / 2.0
assert median == 2.5
Release History

Release History


This version

History Node

TODO: Figure out how to actually get changelog content.

Changelog content for this version goes here.

Donec et mollis dolor. Praesent et diam eget libero egestas mattis sit amet vitae augue. Nam tincidunt congue enim, ut porta lorem lacinia consectetur. Donec ut libero sed arcu vehicula ultricies a non tortor. Lorem ipsum dolor sit amet, consectetur adipiscing elit.

Show More

Download Files

Download Files

TODO: Brief introduction on what you do with files - including link to relevant help section.

File Name & Checksum SHA256 Checksum Help Version File Type Upload Date
mediantracker-1.0.tar.gz (6.4 kB) Copy SHA256 Checksum SHA256 Source Sep 2, 2009

Supported By

WebFaction WebFaction Technical Writing Elastic Elastic Search Pingdom Pingdom Monitoring Dyn Dyn DNS Sentry Sentry Error Logging CloudAMQP CloudAMQP RabbitMQ Heroku Heroku PaaS Kabu Creative Kabu Creative UX & Design Fastly Fastly CDN DigiCert DigiCert EV Certificate Rackspace Rackspace Cloud Servers DreamHost DreamHost Log Hosting