问题描述
我有一个R脚本，可以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都会花费大量时间来重新安装该软件包(实际上确实要花一些时间，因为实际情况中包含多个软件包的向量).
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).
如何首先检查软件包是否已安装，然后仅对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
尝试:require("xtable")或"xtable" %in% rownames(installed.packages())
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