尝试填充R数据框，但使用我的代码失败

Question

我正在从文本文件中读取一些数据，然后从中提取某些句子。最后，我试图使用创建的对象填充数据框，并为此使用for循环。

我尝试为此编写一个循环：

 us_doc1 <- "This is a sample text which has lots of bla bla bla text data. Employee Handbook 2019. docx Page 1."

    us_doc2 <- "This is another sample text which has lots of bla bla bla text data. Employee Handbook 2019. docx Page 2."

    us_docx <- unlist(list(us_doc1, us_doc2))

    usDoc <- data.frame()

    len <- length(us_doc)

    for (i in 1:len) {
     # read every page
     x <- us_doc[i]

     # remove white spaces from the text
     x <- gsub("\\s+", " ", x)

     # grep sentence
     x <- unlist(strsplit(x, "\\."))
     PageRefrence <- x[grep(pattern = "docx Page", x, ignore.case = T)]
  handbook <- x[grep(pattern = "Employee Handbook 2019.docx", x, ignore.case = T)]

     usDoc <- rbind(i, handbook, PageRefrence, x, usDoc)

    }



expected a data frame:

    v1    v2                            v3                  v4
    1     Employee Handbook 2019.docx   docx Page 1         This is a.....
    2     Employee Handbook 2019.docx   docx Page 2         This is another...