小编Zaw*_*min的帖子

install.packages("data.table")
trying URL 'https://cran.rstudio.com/bin/macosx/el-capitan/contrib/3.5/data.table_1.12.8.tgz'
Content type 'application/x-gzip' length 2117137 bytes (2.0 MB)
downloaded 2.0 MB
The downloaded binary packages are in
    /var/folders/r1/1rsn2y0j78v907qgv0btm_fm0000gn/T//RtmppBu3UK/downloaded_packages

使用提供的代码更新到最新的开发版本：

data.table::update.dev.pkg()

打印的控制台：

Warning: unable to access index for repository https://Rdatatable.gitlab.io/data.table/bin/macosx/el-capitan/contrib/3.5:
  cannot open URL 'https://Rdatatable.gitlab.io/data.table/bin/macosx/el-capitan/contrib/3.5/PACKAGES'
Package which is only available in source form, and may need compilation of C/C++/Fortran: ‘data.table’
Do you want to attempt to install these from sources? (Yes/no/cancel) Yes
installing the source package ‘data.table’

trying URL 'https://Rdatatable.gitlab.io/data.table/src/contrib/data.table_1.12.9.tar.gz'
Content type 'application/gzip' length 5189945 bytes (4.9 MB) …

OECD 数据中的 STRATUM 太长，为了简单起见，我使用了这个名称，并希望将其简化为更短和更精确的命名，如下面的代码所示。

pisaMas[,`:=`
             (SchoolType = c(ifelse(STRATUM == "National Secondary School", "Public", 
                                    ifelse(STRATUM == "Religious School", "Religious", 
                                           ifelse(STRATUM == "MOE Technical School", "Technical",0)))))]
pisaMas[,table(SchoolType)]

我想知道是否有一个简单的方法来解决这个问题，使用 data.table 包。

我使用 R 中的 rvest 使用以下代码从本文页面中抓取文本关键字：

#install.packages("xml2") # required for rvest
library("rvest") # for web scraping
library("dplyr") # for data management

#' start with get the link for the web to be scraped
page <- read_html("https://www.sciencedirect.com/science/article/pii/S1877042810004568")
keyW <- page %>% html_nodes("div.Keywords.u-font-serif") %>% html_text() %>% paste(collapse = ",")

它给了我：

> keyW    
[1] "KeywordsPhysics curriculumTurkish education systemfinnish education systemPISAphysics achievement"

使用以下代码行从字符串中删除单词“Keywords”及其之前的所有内容后：

keyW <- gsub(".*Keywords","", keyW)

新的密钥W是：

[1] "Physics curriculumTurkish education systemfinnish education systemPISAphysics achievement"

但是，我想要的输出是这个列表：

[1] "Physics curriculum" "Turkish education system" "finnish education …