问题描述
我有一个 R 脚本，它与不同计算机上的多个用户共享.其中一行包含 install.packages("xtable") 命令.
I have an R script that is shared with several users on different computers. One of its lines contains the install.packages("xtable") command.
问题在于，每次有人运行脚本时，R 显然会花费大量时间重新安装包(实际上确实需要一些时间，因为真实案例有多个包的向量).
The problem is that every time someone runs the script, R spends a great deal of time apparently reinstalling the package (it actually does take some time, since the real case has vector of several packages).
我怎样才能先检查软件包是否已安装，然后只为未安装的软件包运行 install.packages()?
How can I make first check if the packages are installed and then only run install.packages() for the ones that are not?
推荐答案
try: require("xtable") or "xtable" %in% rownames(installed.packages())
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