TM包: UseMethod("TermDocumentMatrix"，x)出错

Question

我想绘制一个术语文档矩阵，如图6所示，位于JSS article on TM包1文章链接：https://www.jstatsoft.org/article/view/v025i05中

我的语料库Speach-English.txt在这里：https://github.com/yushu-liu/speach-english.git

该图应如下所示：

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下面是我的代码：

library(tm)
library(stringr)
library(wordcloud)

text <- paste(readLines("D:/Rdata/speach-English.txt"), collapse = " ")
text_tidy <- gsub(pattern = "\\W",replace=" ",text)
text_tidy2 <- gsub(pattern = "\\d",replace=" ",text_tidy)

text_tidy2 <- tolower(text_tidy2)
text_tidy2 <- removeWords(text_tidy2,stopwords())
text_tidy2 <- gsub(pattern = "\\b[A-z]\\b{1}",replace=" ", text_tidy2 )
text_tidy2 <- stripWhitespace(text_tidy2)

textbag <- str_split(text_tidy2,pattern = "\\s+")
textbag <- unlist(textbag)

tdm <- TermDocumentMatrix(textbag, control = list(removePunctuation = TRUE,
                                                removeNumbers = TRUE,
                                                stopwords = TRUE))

plot(tdm, terms = findFreqTerms(tdm, lowfreq = 6)[1:25], corThreshold = 0.5)

但是有一个bug出来了：

Error in UseMethod("TermDocumentMatrix", x) : 
  no applicable method for 'TermDocumentMatrix' applied to an object of class "character"

为什么？谢谢!