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Haskell Data Analysis Cookbook

By : Nishant Shukla
Book Image

Haskell Data Analysis Cookbook

By: Nishant Shukla

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Haskell Data Analysis Cookbook
Nishant Shukla
Jun, 2014 | 334 pages
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Table of Contents (19 chapters)
Haskell Data Analysis Cookbook
Haskell Data Analysis Cookbook
Credits
Credits
About the Author
About the Author
About the Reviewers
About the Reviewers
www.PacktPub.com
www.PacktPub.com
Preface
Preface
Free Chapter
1
The Hunt for Data
The Hunt for Data
Introduction
Harnessing data from various sources
Accumulating text data from a file path
Catching I/O code faults
Keeping and representing data from a CSV file
Examining a JSON file with the aeson package
Reading an XML file using the HXT package
Capturing table rows from an HTML page
Understanding how to perform HTTP GET requests
Learning how to perform HTTP POST requests
Traversing online directories for data
Using MongoDB queries in Haskell
Reading from a remote MongoDB server
Exploring data from a SQLite database
2
Integrity and Inspection
Integrity and Inspection
Introduction
Trimming excess whitespace
Ignoring punctuation and specific characters
Coping with unexpected or missing input
Validating records by matching regular expressions
Lexing and parsing an e-mail address
Deduplication of nonconflicting data items
Deduplication of conflicting data items
Implementing a frequency table using Data.List
Implementing a frequency table using Data.MultiSet
Computing the Manhattan distance
Computing the Euclidean distance
Comparing scaled data using the Pearson correlation coefficient
Comparing sparse data using cosine similarity
3
The Science of Words
The Science of Words
Introduction
Displaying a number in another base
Reading a number from another base
Searching for a substring using Data.ByteString
Searching a string using the Boyer-Moore-Horspool algorithm
Searching a string using the Rabin-Karp algorithm
Splitting a string on lines, words, or arbitrary tokens
Finding the longest common subsequence
Computing a phonetic code
Computing the edit distance
Computing the Jaro-Winkler distance between two strings
Finding strings within one-edit distance
Fixing spelling mistakes
4
Data Hashing
Data Hashing
Introduction
Hashing a primitive data type
Hashing a custom data type
Running popular cryptographic hash functions
Running a cryptographic checksum on a file
Performing fast comparisons between data types
Using a high-performance hash table
Using Google's CityHash hash functions for strings
Computing a Geohash for location coordinates
Using a bloom filter to remove unique items
Running MurmurHash, a simple but speedy hashing algorithm
Measuring image similarity with perceptual hashes
5
The Dance with Trees
The Dance with Trees
Introduction
Defining a binary tree data type
Defining a rose tree (multiway tree) data type
Traversing a tree depth-first
Traversing a tree breadth-first
Implementing a Foldable instance for a tree
Calculating the height of a tree
Implementing a binary search tree data structure
Verifying the order property of a binary search tree
Using a self-balancing tree
Implementing a min-heap data structure
Encoding a string using a Huffman tree
Decoding a Huffman code
6
Graph Fundamentals
Graph Fundamentals
Introduction
Representing a graph from a list of edges
Representing a graph from an adjacency list
Conducting a topological sort on a graph
Traversing a graph depth-first
Traversing a graph breadth-first
Visualizing a graph using Graphviz
Using Directed Acyclic Word Graphs
Working with hexagonal and square grid networks
Finding maximal cliques in a graph
Determining whether any two graphs are isomorphic
7
Statistics and Analysis
Statistics and Analysis
Introduction
Calculating a moving average
Calculating a moving median
Approximating a linear regression
Approximating a quadratic regression
Obtaining the covariance matrix from samples
Finding all unique pairings in a list
Using the Pearson correlation coefficient
Evaluating a Bayesian network
Creating a data structure for playing cards
Using a Markov chain to generate text
Creating n-grams from a list
Creating a neural network perceptron
8
Clustering and Classification
Clustering and Classification
Introduction
Implementing the k-means clustering algorithm
Implementing hierarchical clustering
Using a hierarchical clustering library
Finding the number of clusters
Clustering words by their lexemes
Classifying the parts of speech of words
Identifying key words in a corpus of text
Training a parts-of-speech tagger
Implementing a decision tree classifier
Implementing a k-Nearest Neighbors classifier
Visualizing points using Graphics.EasyPlot
9
Parallel and Concurrent Design
Parallel and Concurrent Design
Introduction
Using the Haskell Runtime System options
Evaluating a procedure in parallel
Controlling parallel algorithms in sequence
Forking I/O actions for concurrency
Communicating with a forked I/O action
Killing forked threads
Parallelizing pure functions using the Par monad
Mapping over a list in parallel
Accessing tuple elements in parallel
Implementing MapReduce to count word frequencies
Manipulating images in parallel using Repa
Benchmarking runtime performance in Haskell
Using the criterion package to measure performance
Benchmarking runtime performance in the terminal
10
Real-time Data
Real-time Data
Introduction
Streaming Twitter for real-time sentiment analysis
Reading IRC chat room messages
Responding to IRC messages
Polling a web server for latest updates
Detecting real-time file directory changes
Communicating in real time through sockets
Detecting faces and eyes through a camera stream
Streaming camera frames for template matching
11
Visualizing Data
Visualizing Data
Introduction
Plotting a line chart using Google's Chart API
Plotting a pie chart using Google's Chart API
Plotting bar graphs using Google's Chart API
Displaying a line graph using gnuplot
Displaying a scatter plot of two-dimensional points
Interacting with points in a three-dimensional space
Visualizing a graph network
Customizing the looks of a graph network diagram
Rendering a bar graph in JavaScript using D3.js
Rendering a scatter plot in JavaScript using D3.js
Diagramming a path from a list of vectors
12
Exporting and Presenting
Exporting and Presenting
Introduction
Exporting data to a CSV file
Exporting data as JSON
Using SQLite to store data
Saving data to a MongoDB database
Presenting results in an HTML web page
Creating a LaTeX table to display results
Personalizing messages using a text template
Exporting matrix values to a file
Index
Index

Encoding a string using a Huffman tree

A Huffman tree allows efficient encoding of data by calculating a probability distribution of characters to optimize the space taken per character. Imagine compressing this book into one piece of paper and back without any information loss. Huffman trees allow this type of optimal lossless data compression based on statistics.

In this recipe, we will implement a Huffman tree from a source of text and produce a string representation of its Huffman codes.

For example, the string "hello world" contains 11 characters, which, depending on the encoding and architecture, may take up as few as 11 bytes of space to represent. The code in this recipe will transform the string into just 51 bits, or 6.375 bytes.

Getting ready

Make sure to be connected to the Internet since this recipe will download text from http://norgiv.com/big.txt to analyze probability distribution of many characters. We will be using the min-heap that was implemented in the previous recipe by...

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