我在R中使用stringr，并且有一串文字列出了新闻标题。我想提取这些标题，但只显示出现的前N个标题。在我的示例字符串中，我有三个文章标题，但是我只想提取前两个标题。

如何告诉str_extract仅收集前2个标题？谢谢。

这是我当前的示例文本代码。

library(stringr)

这是示例文本。

texting <- ("Time: Friday,September 14,2018 4:34:00 PM EDT\r\nJob Number: 73591483\r\nDocuments (100)\r\n 1. U.S. Stocks Rebound Slightly After Tech-Driven Slump\r\n   Client/Matter: -None-\r\n   Search Terms: trade war or US-China trade or china tariff and not dealbook\r\n   Search Type: Terms and Connectors\r\n   Narrowed by:\r\n             Content Type                         Narrowed by\r\n             News                                 Sources: The New York Times; Content Type: News;\r\n                                                  Timeline: Jan 01,2018 to Dec 31,2018\r\n 2. Shifting Strategy on Tariffs\r\n   Client/Matter: -None-\r\n   Search Terms: trade war or US-China trade or china tariff and not dealbook\r\n 100. Example")

titles.1 <- str_extract_all(texting,"\\d+\\.\\s.+")
titles.1

当前代码带回字符串中的所有三个匹配项：

[[1]]

[1] "1. U.S. Stocks Rebound Slightly After Tech-Driven Slump"

[2] "2. Shifting Strategy on Tariffs"                        

[3] "100. Example"

我只希望它收集前两场比赛。