Handling and Processing Strings in R

Posted on September 22, 2013

Handling and Processing Strings in R is an ebook dedicated to show you some introductory material to manipulate character strings in R.

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Why this ebook?

Many years ago I decided to apply for a job in a company that developed data mining applications for big retailers. I was invited for an on-site visit and I went through the typical series of interviews with the members of the analytics team. Everything was going smoothly and I was enjoying all the conversations. Then it came turn to meet the computer scientist. After briefly describing his role in the team he started asking me a bunch of technical questions and tests. Although I was able to answer those questions related with statistics and multivariate analysis, I had a really hard time trying to answer a series of questions related with string manipulations.

I will remember my interview with that guy as one of the most embarrassing moments of my life. That day, the first thing I did when I went back home was to open my laptop, launch R, and start reproducing the tests I failed to solve. It didn’t take me that much to get the right answers. Unfortunately, it was too late and the harm was already done. Needless to say I wasn’t offered the job. That shocking experience showed me that I was not prepared for manipulating character strings. I felt so bad that I promised myself to learn the basics of strings manipulation and text processing. “Handling and Processing Strings in R” is one of the derived results of that old promise.

The content of this ebook is the byproduct of my experience working with character string data in R. It is based on my notes, scripts, projects, and uncountable days and nights in which I’ve been struggling with text data. Briefly, I’ve tried to document and organize several topics related with manipulating character strings.

Handling and Processing Strings in R in a nutshell

Although this is not a complete list of the topics covered in the manuscript, here are some of the functions that are discussed in the ebook:

Basic functions

• character() creating a character vector
• is.character() test character mode
• as.character() convert as character
• paste() pasting

Printing related functions

• print() generic printing
• noquote() unquoted characters
• cat() concatenate and print
• format() special formats
• sprintf() C-style string formatting
• toString() convert to string objects

Basic String Manipulations

• char() count number of characters
• tolower() convert to lower case
• toupper() convert to upper case
• casefold() case folding
• chartr() character translation
• abbreviate() abbreviation
• substring() substrings of a character vector
• substr() substrings of a character vector

String Manipulations with stringr

• str_c() concatenation
• str_length() number of characters
• str_sub() substring
• str_dup() string duplication
• str_pad() string padding
• str_wrap() string wrapping
• str_trim() trimming whitespaces
• word() extract words from a sentence

Functions for Regular Expressions

• grep()
• grepl()
• regexpr()
• gregexpr()
• regexec()
• sub()
• gsub()
• strsplit()
• str_detect()
• str_extract()
• str_extract_all()
• str_match()
• str_match_all()
• str_locate()
• str_locate_all()
• str_replace()
• str_replace_all()
• str_split()
• str_split_fixed()