# List of packages for session
.packages = c("ggplot2", "plyr", "rms")

# Install CRAN packages (if not already installed)
.inst <- .packages %in% installed.packages()
if(length(.packages[!.inst]) > 0) install.packages(.packages[!.inst])

# Load packages into session 
lapply(.packages, require, character.only=TRUE)

今天，我偶然发现了rlang包提供的两个方便函数，即is_installed()和check_installed()。

从帮助页面(强调添加):

These functions check that packages are installed with minimal side effects. If installed, the packages will be loaded but not attached. is_installed() doesn't interact with the user. It simply returns TRUE or FALSE depending on whether the packages are installed. In interactive sessions, check_installed() asks the user whether to install missing packages. If the user accepts, the packages are installed [...]. If the session is non interactive or if the user chooses not to install the packages, the current evaluation is aborted.

interactive()
#> [1] FALSE
rlang::is_installed(c("dplyr"))
#> [1] TRUE
rlang::is_installed(c("foobarbaz"))
#> [1] FALSE
rlang::check_installed(c("dplyr"))
rlang::check_installed(c("foobarbaz"))
#> Error:
#> ! The package `foobarbaz` is required.

由reprex包在2022-03-25创建(v2.0.1)

你可以使用require的返回值:

if(!require(somepackage)){
    install.packages("somepackage")
    library(somepackage)
}

我在安装后使用library，因为如果安装不成功或由于其他原因无法加载包，它将抛出异常。您可以使其更加健壮和可重用:

dynamic_require <- function(package){
  if(eval(parse(text=paste("require(",package,")")))) return(TRUE)
  
  install.packages(package)
  return(eval(parse(text=paste("require(",package,")"))))
}

此方法的缺点是必须以引号传递包名，而对于真正的require则不这样做。

确定。

您需要比较“已安装的包”和“所需的包”。这非常接近于我用蔓越莓做的事情，因为我需要比较“存储的已知包”和“当前已知的包”，以确定新的和/或更新的包。

就像这样

AP <- available.packages(contrib.url(repos[i,"url"]))   # available t repos[i]

为了获得所有已知的包，模拟调用当前安装的包，并将其与给定的目标包集进行比较。

pckg=c("shiny","ggplot2","dplyr","leaflet","lubridate","RColorBrewer","plotly","DT","shinythemes")

for(i in 1:length(pckg)) 
   {
      print(pckg[i])
      if (!is.element(pckg[i], installed.packages()[,1]))
      install.packages(pckg[i], dep = TRUE)
      require(pckg[i], character.only = TRUE)
}

library <- function(x){
  x = toString(substitute(x))
if(!require(x,character.only=TRUE)){
  install.packages(x)
  base::library(x,character.only=TRUE)
}}

这适用于不带引号的包名，并且相当优雅(参见GeoObserver的答案)