Savanna Outliers: Plug & Play Anomaly Detection

This package allows to detect outliers using Grubb's test for outliers. Supports hashes and arrays as inputs.

Grubb's test (named after Frank E. Grubbs), also known as the maximum normed residual test or extreme studentized deviate test, is a statistical test used to detect outliers in a univariate data set assumed to come from a normally distributed population.

Installation

gem install savanna-outliers

Usage

Require package at the beginning of the document.

require 'savanna-outliers'

Arrays

Discovering Outliers

##
# Identify any outliers existance
some_array = [10, 12, 8, 11, 9, 13, 12, 10, 1000, 12, 10, 1100, 9, 5000]
Savanna::Outliers.any_outliers?(some_array, :all) # => true

##
# Identify max outliers existance
some_array = [10, 12, 8, 11, 9, 13, 12, 10, 1000, 12, 10, 1100, 9, 5000]
Savanna::Outliers.any_outliers?(some_array, :max) # => true

##
# Identify min outliers existance
some_array = [10, 12, 8, 11, 9, 13, 12, 10, -1000, 12, 10, -1100, 9, -5000]
Savanna::Outliers.any_outliers?(some_array, :min) # => true

Getting Outliers

##
# Get all outliers from array
some_array = [10, 12, 8, 11, 9, 13, 12, 10, -1000, 1000, 12, 10, 9]
Savanna::Outliers.get_outliers(some_array, :all) # => [1000, -1000]

##
# Get max outliers from array
some_array = [10, 12, 8, 11, 9, 13, 12, 10, 1000, 12, 10, 1100, 9, 5000]
Savanna::Outliers.get_outliers(some_array, :max) # => [5000, 1100, 1000]

##
# Get min outliers from array
some_array = [10, 12, 8, 11, 9, 13, 12, 10, -1000, 12, 10, -1100, 9, -5000]
Savanna::Outliers.get_outliers(some_array, :min) # => [-5000, -1100, -1000]

Removing Outliers

##
# Remove all outliers from array
some_array = [10, 12, 8, 11, 9, 13, 12, 10, -1000, 1000, 12, 10, 9]
Savanna::Outliers.remove_outliers(some_array, :all) # => [10, 12, 8, 11, 9, 13, 12, 10, 12, 10, 9]

##
# Remove max outliers from array
some_array = [10, 12, 8, 11, 9, 13, 12, 10, 1000, 12, 10, 1100, 9, 5000]
Savanna::Outliers.remove_outliers(some_array, :max) # => [10, 12, 8, 11, 9, 13, 12, 10, 12, 10, 9]

##
# Remove min outliers from array
some_array = [10, 12, 8, 11, 9, 13, 12, 10, -1000, 12, 10, -1100, 9, -5000]
Savanna::Outliers.remove_outliers(some_array, :min) # => [10, 12, 8, 11, 9, 13, 12, 10, 12, 10, 9]

Hashes

Discovering Outliers

##
# Identify any outliers existance
some_hash = {a: 10, b: 12, c: 8, d: 11, e: 9, f: 13, g: 12, h: 10, i: 1000, j: 12, k: 10, l: 1100, m: 9, n: 5000}
Savanna::Outliers.any_outliers?(some_hash, :all) # => true

##
# Identify max outliers existance
some_hash = {a: 10, b: 12, c: 8, d: 11, e: 9, f: 13, g: 12, h: 10, i: 1000, j: 12, k: 10, l: 1100, m: 9, n: 5000}
Savanna::Outliers.any_outliers?(some_hash, :max) # => true

##
# Identify min outliers existance
some_hash = {a: 10, b: 12, c: 8, d: 11, e: 9, f: 13, g: 12, h: 10, i: -1000, j: 12, k: 10, l: -1100, m: 9, n: -5000}
Savanna::Outliers.any_outliers?(some_hash, :min) # => true

Getting Outliers

##
# Get all outliers from hash
some_hash = {a: 10, b: 12, c: 8, d: 11, e: 9, f: 13, g: 12, h: 10, i: -1000, j: 1000, k: 12, l: 10, m: 9}
Savanna::Outliers.get_outliers(some_hash, :all) # => {j: 1000, i: -1000}

##
# Get max outliers from hash
some_hash = {a: 10, b: 12, c: 8, d: 11, e: 9, f: 13, g: 12, h: 10, i: 1000, j: 12, k: 10, l: 1100, m: 9, n: 5000}
Savanna::Outliers.get_outliers(some_hash, :max) # => {n: 5000, l: 1100, i: 1000}

##
# Get min outliers from hash
some_hash = {a: 10, b: 12, c: 8, d: 11, e: 9, f: 13, g: 12, h: 10, i: -1000, j: 12, k: 10, l: -1100, m: 9, n: -5000}
Savanna::Outliers.get_outliers(some_hash, :min) # => {n: -5000, l: -1100, i: -1000}

Removing Outliers

##
# Remove max outliers from hash
some_hash = {a: 10, b: 12, c: 8, d: 11, e: 9, f: 13, g: 12, h: 10, i: 1000, j: 12, k: 10, l: 1100, m: 9, n: 5000}
Savanna::Outliers.remove_outliers(some_hash, :max) # => {a: 10, b: 12, c: 8, d: 11, e: 9, f: 13, g: 12, h: 10, j: 12, k: 10, m: 9}

##
# Remove min outliers from hash
some_hash = {a: 10, b: 12, c: 8, d: 11, e: 9, f: 13, g: 12, h: 10, i: -1000, j: 12, k: 10, l: -1100, m: 9, n: -5000}
Savanna::Outliers.remove_outliers(some_hash, :min) # => {a: 10, b: 12, c: 8, d: 11, e: 9, f: 13, g: 12, h: 10, j: 12, k: 10, m: 9}

##
# Remove all outliers from hash
some_hash = {a: 10, b: 12, c: 8, d: 11, e: 9, f: 13, g: 12, h: 10, i: -1000, j: 1000, k: 12, l: 10, m: 9}
Savanna::Outliers.remove_outliers(some_hash, :all) # => {a: 10, b: 12, c: 8, d: 11, e: 9, f: 13, g: 12, h: 10, k: 12, l: 10, m: 9}

License

The MIT License

Copyright (c) 2013 Max Makarochkin

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.