此处的关键是在文本中找到指示您想要的文本开头的标记，以及指示其结尾的标记。这可以是一组使用regex分隔的条件|。
保留第一个标记之前的所有内容（默认情况下），您可以使用删除结尾标记之后的文本，方法是将其从语料库中删除corpus_subset()。在您发现实际数据中的各种模式之后，毫无疑问，实际模式将需要进行调整。
这是我为您的示例文档执行的操作：
library("quanteda")
## Package version: 2.0.0
corp <- readtext::readtext("https://www.sec.gov/Archives/edgar/data/75488/000114036117038612/0001140361-17-038612.txt") %>%
corpus()
# clean up text
corp <- gsub("<.*?>|&#\\d+;", "", corp)
corp <- gsub("&", "&", corp)
corp <- corpus_segment(corp,
pattern = "Item 8\\.01 Other Events\\.|SIGNATURES",
valuetype = "regex"
) %>%
corpus_subset(pattern != "SIGNATURES")
print(corp, max_nchar = -1)
## Corpus consisting of 1 document and 1 docvar.
## 0001140361-17-038612.txt.1 :
## "Investigation of Northern California Fires Since October 8, 2017, several catastrophic wildfires have started and remain active in Northern California. The causes of these fires are being investigated by the California Department of Forestry and Fire Protection (Cal Fire), including the possible role of power lines and other facilities of Pacific Gas and Electric Companys (the Utility), a subsidiary of PG&E Corporation. It currently is unknown whether the Utility would have any liability associated with these fires. The Utility has approximately $800 million in liability insurance for potential losses that may result from these fires. If the amount of insurance is insufficient to cover the Utility's liability or if insurance is otherwise unavailable, PG&E Corporations and the Utilitys financial condition or results of operations could be materially affected."