README.md
# Measurable
[](https://travis-ci.org/agarie/measurable)
[](https://codeclimate.com/github/agarie/measurable)
A gem to test what metric is best for certain kinds of datasets in machine
learning. Besides the `Array` class, I also want to support
[NMatrix](http://github.com/sciruby/nmatrix).
This is a fork of the gem [Distance Measure](https://github.com/reddavis/Distance-Measures),
which has a similar objective, but isn't actively maintained and doesn't support
NMatrix. Thank you, [@reddavis][reddavis]. :)
## Installation
`gem install measurable`
I test this gem (via Travis CI) on Ruby MRI 2.5, 2.6 and 2.7.
## Available distance measures
I'm using the term "distance measure" without much concern for the strict
mathematical definition of a metric. If the documentation for one of the
methods isn't clear about it being or not a metric, please open an issue.
The following are the similarity measures supported at the moment:
- Euclidean distance
- Squared euclidean distance
- Cosine distance
- Max-min distance (from ["K-Means clustering using max-min distance measure"][maxmin])
- Jaccard distance
- Tanimoto distance
- Haversine distance
- Minkowski (aka Cityblock or Manhattan) distance
- Chebyshev distance
- Hamming distance
- [Levenshtein distance](http://en.wikipedia.org/wiki/Levenshtein_distance)
- [Kullback-Leibler divergence](http://en.wikipedia.org/wiki/Kullback%E2%80%93Leibler_divergence)
## How to use
The API I intend to support is something like this:
```ruby
require 'measurable'
# Calculate the distance between two points in space.
Measurable.euclidean([1, 1], [0, 0]) # => 1.41421
# Calculate the norm of a vector, i.e. its distance from the origin.
Measurable.euclidean([1, 1]) # => 1.4142135623730951
# Get the cosine distance between
Measurable.cosine_distance([1, 2], [2, 3]) # => 0.007722123286332261
# Calculate sum of squares directly.
Measurable.euclidean_squared([3, 4]) # => 25
```
Most of the methods accept arbitrary enumerable objects instead of Arrays. For example, it's possible to use [NMatrix](https://github.com/sciruby/nmatrix).
## Documentation
The documentation is hosted on [rubydoc](http://www.rubydoc.info/github/agarie/measurable).
## License
See LICENSE for details.
The original `distance_measures` gem is copyrighted by [@reddavis][reddavis].
[maxmin]: http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=05156398
[reddavis]: (https://github.com/reddavis)