Configure Character Encoding for R under Linux and Windows

R is so powerful and elegant, that attacts more and more people switch to it. Those users come from different places, speack different languages and possiblely use other statistical softwares. So they may encounter one anoying problem: garbled text or unrecognizable characters! For example, some Chinese user wrote a script including variable names in Chinese, and his English colleage’s computer can’t show those character correctly, and can’t run the script under R. Such kind of problem can be categorized as: Character Encoding problem. In the following context, I will share my experience of how to configure character encoding for R under Linux and Windows. Before we go further, let’t take a look of the basic concept of character encoding.

There are thousands of hundrads of characters in this world, like LatinÆ characters, *Arabic charaters, Chinese, Korean, etc. How to store and show them in computer? Yes, character encoding. The most widely known encoding called ASCII, which was invented at the beginning of computer techniqure. ASCII uses one byte to store the numbers 0-9, the letters a-z and A-Z, and some basic punctuation symbols, etc. ASCII encoding includes 128 (2^7) characters in total. We know that computer use Byte as the basic store unit, one byte has 8 bits (2^8 = 256), and ASCII used only half of them, why? I guess at that time the 128 characters are the most used characters, and the inventors may believe that’s enought for daily tasks. With the developement of computer technology, more and more characters need to be stored and shown in computer, the ASCII encoding can’t meet the demands. So some other character encodings were invented. For example, the ISO-8859-1 encoding, which also is called Latin-1, is widlely used in Enroupe. ISO-8859-1 can be taken as a superset of ASCII, which mean the characters encoded in ASCII can also be displayed correctly in ISO-8859-1, but the not the opposite version. Note, if the characters encoded in ISO-8859-1 contains only the characters supported by ASCII, these characters can still be displayed correctly in ASCII. ISO-8859-1 uses 8-bit byte to store characters, but the total characters ISO-8859-1 supported is not 256 (2^8), that’s because somes range of bits were not used. Perhaps, the inventors believe those characters are enough. Windows-1252 is another character encoding, similiar to ISO-8859-1 but contains more characters, because it used total bits. So Windows-1252 can be taken as the supperset of ISO-8859-1. But there are more characters than 256, e.g. Chinese contains thousands of characters, and many other kinds of lanuages also contain numerous characters. To solve this problem, Unicode was invented. The newest Unicode encoding uses 4 bytes, and have encoded more than 110000 characters, contains almost all writing characters. So, why not all computers use Unicode encoding, and people will not worry about garbled text? There are several reasons, but the obvious one is it waste too much storage space. For example, a European computer may use only Latin characters, why waste three times storage space to save all characters using Unicode? The usage of different character encoding lead to the prolbem of garbed text! Ok, now let’s back to the configuration of character encoding for R.

When encounter garbed text in R, we should first check the encoding type of R. I will show how to check and setup encoding under Linux and Windows.

###1. Under Linux Under Linux, we start R programe by typing R in terminal (which can be called up by press Ctrl+Alt+T). To check the current encoding, we use the command Sys.getlocale(). This command will list the current locale setting, including LC_CTYPE, LC_NUMERIC, etc.

> Sys.getlocale()

For example, LC_CTYPE=nb_NO.ISO-8859-1 means the current locale (LC_) for character type (CTYPE) is nb_NO.ISO-8859-1. nb_NO.ISO-8859-1 contains the information for language (nb means Norwegian (Bokmål)), region (NO means Norway) and character encoding seperated with dot (ISO-8859-1).

Ok, this is the current character encoding, and I encountered the garbed text problem, how to change the encoding to show text correctly, suppose I know the script was writen by a Chinese? There is function is R called Sys.setlocale can do the configuration. But wait! What’s the correct string for the locale I want to setup? I know one encoding for Chinese character is CP18030, should I type “zh_CN.CP-18030” or “zh_CN.WINDOWS-18030”, or something else? I mean where I can find a list contains the information of language and corresponding string? In R, there is no such a function, but we can get them in Linux. In Linux’s terminal, type locale will list current locale setting:

tian@tian-VirtualBox:~$ locale

Type locale -a will list all the encoding types Linux have installed. Go through them to see if the language you are looking for has already been there.

tian@tian-VirtualBox:~$ locale -a

If it’s not there, then we need to install it, and before we start to install we should first know the name of the locale, which should be in the list of supported locales of Linux. Type less /usr/share/i18n/SUPPORTED will list all the supported locales, choose the one you want and generate it using the command: sudo locale-gen. E.g sudolocale-gen nb_NO will install the Norwegian (Bokmål) for Norway. It didn’t show the character encoding type, because by default Norwegian (Bokmål) using ISO-8859-1. Update the generated locale to system using command: sudo update-locale. Now the locale has been installed to computer, but we still didn’t make it as the default system locale. We can change the default locale by editing the file /etc/default/locale to the locale we wanted.

sudo nano /etc/default/locale

Save the change and restart the computer, you can check the current locale setting using locale command.

By default, R will use the locale setting of the operation system. So if we type command Sys.getlocale() in R console, the installed locale setting will be displayed. R also has a function for temporary setting of locale: Sys.setlocale. If the current locale setting can not show some script correctly, we need to guess which locale is suitable, so we use Sys.setlocale. For example, Sys.setlocale(category = "LC_ALL", locale = "zh_CN.utf-8") will change current locale to Chinese (Simplified)_People’s Republic of China using character encoding “UTF-8”. Note, this changes the locale temporary, when you quit R and restart it again, the locale is still the system’s locale.

###2. Under Windows The configuration of locale under Windows is a bit less concise than under Linux.

We can get the current locale in R using Sys.getlocale().

> Sys.getlocale()
[1] "LC_COLLATE=Norwegian (Bokmål)_Norway.1252;LC_CTYPE=Norwegian (Bokmål)_Norway.1252;LC_MONETARY=Norwegian (Bokmål)_Norway.1252;LC_NUMERIC=C;LC_TIME=Norwegian (Bokmål)_Norway.1252"

Note, the displayed locale details are a little different with the ones under Linux. For example, LC_CTYPE=Norwegian (Bokmål)_Norway.1252 means Norwegian Bokmål for Norway using codepage 1252. The new term codepage is actually the character encoding used for Windows. For example codepage ‘936’ means the character encoding for GB18030 which is a Chinese character encoding. Unlike Linux, Windows supplies only one encoding for each language.

If I want to change current locale to Chinese, how should I proceed? Well, we can change the locale in Windows’ Control Panel -> Region and Language -> Format, choose the format you want, e.g. “Chinese (Simplified, PRC)”, and apply change. Now, restart R and check the locale information using command Sys.getlocale(). We can see the default locale for R is “Chinese (Simplified)_People’s Republic of China.936”, and the code page ‘936’ is the character encoding “GB18030”.

> Sys.getlocale()
[1] "LC_COLLATE=Chinese (Simplified)_People's Republic of China.936;LC_CTYPE=Chinese (Simplified)_People's Republic of China.936;LC_MONETARY=Chinese (Simplified)_People's Republic of China.936;LC_NUMERIC=C;LC_TIME=Chinese (Simplified)_People's Republic of China.936"

What’s if we want to change the locale temporary in R? For example, we need to set the encoding for traditional Chinese instead of Simplified Chinese, Can we use the command: Sys.setlocale(category = "LC_ALL", locale = "Chinese (Traditional)_People's Republic of China.936")? Yes, you can. But it doesn’t work! Why? That’s because ‘936’ is the encoding for simplified chinese characters not for traditional chinese characters. Then you want a list of available locales to determine the legal locale options. Unlike Linux, we can’t (or have no easy method to) find such list. But you can find the list by searching Windows Language strings on internet. The currently language strings list can be found here. The “Language string” column contains the legal input for setting locale in R. For example, if I want to change current locale to Traditional Chinese, I use command: Sys.setlocale(category = "LC_ALL", locale = "cht").

> Sys.setlocale(category = "LC_ALL", locale = "cht")
[1] "LC_COLLATE=Chinese (Traditional)_Taiwan.950;LC_CTYPE=Chinese (Traditional)_Taiwan.950;LC_MONETARY=Chinese (Traditional)_Taiwan.950;LC_NUMERIC=C;LC_TIME=Chinese (Traditional)_Taiwan.950"

Check the current locale setting, we can see it changed to “LC_CTYPE=Chinese (Traditional)_Taiwan.950;LC_MONETARY=Chinese (Traditional)_Taiwan.950”, where codepage ‘950’ is encoding Big5. Windows uses only one character encoding for each language, which make the recognization of encoding type easy.

If I received a script contains Simplified Chinese characters and generated under Windows OS, the encoding must be GB18030. To show it correctly, I can set or change the locale of R to “chinese”, and import the source code using readLines, or there is a even easy way: using Office Word! If using RStudio as the editor for R, we just need to change the default encoding to “GB18030” in “Tools -> Options -> General -> Default text encoding”. Apply the setting, then open the script, it should be displayed correctly.

Written on November 15, 2013