使用tm()从R中的语料库中删除非英语文本

Question

我在R中使用tm()和wordcloud()进行一些基本的数据挖掘,但由于我的数据集中有非英文字符(即使我试图根据背景变量过滤掉其他语言),我遇到了困难.

假设我的TXT文件中的一些行(在TextWrangler中保存为UTF-8)如下所示:

Special
satisfação
Happy
Sad
Potential für

然后我将我的txt文件读入R:

words <- Corpus(DirSource("~/temp", encoding = "UTF-8"),readerControl = list(language = "lat"))

这会产生警告消息:

Warning message:
In readLines(y, encoding = x$Encoding) :
  incomplete final line found on '/temp/file.txt'

但由于这是一个警告,而不是错误,我继续向前推进.

words <- tm_map(words, stripWhitespace)
words <- tm_map(words, tolower)

然后产生错误:

Error in FUN(X[[1L]], ...) : invalid input 'satisfa??o' in 'utf8towcs'

我愿意找到在TextWrangler或R中过滤掉非英文字符的方法; 无论什么是最权宜之计.谢谢你的帮助!

Answer 1

这是一种在创建语料库之前删除包含非ASCII字符的单词的方法:

# remove words with non-ASCII characters
# assuming you read your txt file in as a vector, eg. 
# dat <- readLines('~/temp/dat.txt')
dat <- "Special,  satisfação, Happy, Sad, Potential, für"
# convert string to vector of words
dat2 <- unlist(strsplit(dat, split=", "))
# find indices of words with non-ASCII characters
dat3 <- grep("dat2", iconv(dat2, "latin1", "ASCII", sub="dat2"))
# subset original vector of words to exclude words with non-ASCII char
dat4 <- dat2[-dat3]
# convert vector back to a string
dat5 <- paste(dat4, collapse = ", ")
# make corpus
require(tm)
words1 <- Corpus(VectorSource(dat5))
inspect(words1)

A corpus with 1 text document

The metadata consists of 2 tag-value pairs and a data frame
Available tags are:
  create_date creator 
Available variables in the data frame are:
  MetaID 

[[1]]
Special, Happy, Sad, Potential