r - 下标越界。提取 PDF

Question

我正在从 pdf 中提取文本。删除标点符号并查看重复的关键单词以及它们出现的频率。

library(pdftools)
library(tm)

setwd("S:/Shared Folders/Impact Investing/Investment/Scripts/PDF")

files <- list.files(pattern = "pdf$")
opinions <- lapply(files, pdf_text)

corp <- Corpus(URISource(files),
           readerControl = list(reader = readPDF))

opinions.tdm <- TermDocumentMatrix(corp, 
        control = 
            list(removePunctuation = TRUE,
            stopwords = TRUE,
            tolower = TRUE,
            stemming = TRUE,
            removeNumbers = TRUE,
            bounds = list(global = c(3, Inf)))) 

inspect(opinions.tdm[1:10,])

我目前收到一个错误：

(opinions.tdm, 1:10, )中的错误[.simple_triplet_matrix：下标越界

我opinions.tdm的有以下特点：

opinion.tdm 列表长度为 6。nrow 整数 [1]。ncol [1]。暗名列表 [2]。属性 [3]