转换删除 R 中的文档错误

Question

每当我运行此代码时，tm_map 行都会给我警告消息作为警告消息：在 tm_map.SimpleCorpus(docs, toSpace, "/") 中：转换丢弃文档

texts <- read.csv("./Data/fast food/Domino's/Domino's veg pizza.csv",stringsAsFactors = FALSE)
        docs <- Corpus(VectorSource(texts))
        toSpace <- content_transformer(function (x , pattern ) gsub(pattern, " ", x))
        docs <- tm_map(docs, toSpace, "/")
        docs <- tm_map(docs, toSpace, "@")
        docs <- tm_map(docs, toSpace, "\\|")
        docs <- tm_map(docs, content_transformer(tolower))
        docs <- tm_map(docs, removeNumbers)
        docs <- tm_map(docs, removeWords, stopwords("english"))
        docs <- tm_map(docs, removeWords, c("blabla1", "blabla2")) 
        docs <- tm_map(docs, removePunctuation)
        docs <- tm_map(docs, stripWhitespace)

Answer 1

此警告仅在您用于content_transformer创建自己的特定函数时出现。它仅在您拥有基于VectorSource.

原因是底层代码有检查，看语料内容的名称个数是否与语料内容的长度匹配。将文本作为向量读取时，没有文档名称，并且会弹出此警告。这只是一个警告，没有文件被丢弃。

请参阅以下示例：

text <- c("this is my text with a forward slash / and some other text")
library(tm)
toSpace <- content_transformer(function (x , pattern ) gsub(pattern, " ", x))

text <- c("this is my text with a forward slash / and some other text")
text_corpus <- Corpus(VectorSource(text))
inspect(text_corpus)
<<SimpleCorpus>>
Metadata:  corpus specific: 1, document level (indexed): 0
Content:  documents: 1

[1] this is my text with a forward slash / and some other text

# warning appears here
text_corpus <- tm_map(text_corpus, toSpace, "/")
inspect(text_corpus)
<<SimpleCorpus>>
Metadata:  corpus specific: 1, document level (indexed): 0
Content:  documents: 1

[1] this is my text with a forward slash   and some other text

您可以使用以下命令看到 text_corpus 中没有名称：

names(content(text_corpus))
NULL

如果您不希望出现此警告，则需要创建一个 data.frame 并将其用作DataframeSource.

text <- c("this is my text with a forward slash / and some other text")
doc_ids <- c(1)

df <- data.frame(doc_id = doc_ids, text = text, stringsAsFactors = FALSE)
df_corpus <- Corpus(DataframeSource(df))
inspect(df_corpus)
# no warning appears
df_corpus <- tm_map(df_corpus, toSpace, "/")
inspect(df_corpus)

names(content(df_corpus))
"1"