blocks|key|646471|text|试试：require("xtable")或"xtable"+%25in%25+rownames(installed.packages())|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|646472|entityMap^0|3|H|L|18|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|M|8|@]|D|@]|E|$]]]|G|$]]

try: <code>require("xtable")</code> or <code>"xtable" %in% rownames(installed.packages())</code>

blocks|key|432511|text|如果你想尽可能简单地做到这一点：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|432512|packages+<-+c("ggplot2",+"dplyr",+"Hmisc",+"lme4",+"arm",+"lattice",+"lavaan")

install.packages(setdiff(packages,+rownames(installed.packages())))++|code-block|syntax|javascript|432513|将第一行中列出的包替换为运行代码所需的包，瞧！|432514|注意:由于Artem下面的评论，编辑后删除了条件包装器。|432515|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|P|8|@]|9|@]|A|$]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

If you want to do it as simply as possible:
<pre><code>packages &lt;- c(&quot;ggplot2&quot;, &quot;dplyr&quot;, &quot;Hmisc&quot;, &quot;lme4&quot;, &quot;arm&quot;, &quot;lattice&quot;, &quot;lavaan&quot;)

install.packages(setdiff(packages, rownames(installed.packages()))) 
</code></pre>
Replace the packages listed on the first line by those needed to run your code, and voilà!
Note: Edited to remove conditional wrapper thanks to Artem's comment below.

blocks|key|432194|text|这是我经常使用的一个函数，用于检查包，否则安装它，然后再次加载：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|432195|pkgTest+<-+function(x)
++{
++++if+(!require(x,character.only+=+TRUE))
++++{
++++++install.packages(x,dep=TRUE)
++++++++if(!require(x,character.only+=+TRUE))+stop("Package+not+found")
++++}
++}|code-block|syntax|javascript|432196|其工作方式类似于pkgTest("xtable")。它只有在设置了镜像的情况下才能工作，但您可以在require调用中输入它。|offset|length|style|CODE|432197|entityMap^0|0|0|8|H|1D|7|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@$I|R|J|S|K|L]|$I|T|J|U|K|L]]|9|@]|A|$]]|$1|M|3|-4|5|6|7|V|8|@]|9|@]|A|$]]]|N|$]]

This is a function I often used to check for a package, install it otherwise and load again:

<pre><code>pkgTest &lt;- function(x)
 {
 if (!require(x,character.only = TRUE))
 {
 install.packages(x,dep=TRUE)
 if(!require(x,character.only = TRUE)) stop("Package not found")
 }
 }
</code></pre>

Works like <code>pkgTest("xtable")</code>. It only works if the mirror is set though, but you could enter that in the <code>require</code> calls.

blocks|key|647052|text|我建议使用system.file的更轻量级的解决方案。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|647053|is_inst+<-+function(pkg)+{
++++nzchar(system.file(package+=+pkg))
}

is_inst2+<-+function(pkg)+{
++++pkg+%25in%25+rownames(installed.packages())
}

library(microbenchmark)
microbenchmark(is_inst("aaa"),+is_inst2("aaa"))
##+Unit:+microseconds
##++++++++++++expr++++++min++++++++lq+++++++mean++++median+++++++uq+++++++max+neval
##++is_inst("aaa")+++22.284+++24.6335+++42.84806+++34.6815+++47.566+++252.568+++100
##+is_inst2("aaa")+1099.334+1220.5510+1778.57019+1401.5095+1829.973+17653.148+++100
microbenchmark(is_inst("ggplot2"),+is_inst2("ggplot2"))
##+Unit:+microseconds
##++++++++++++++++expr++++++min+++++++lq+++++mean+++median+++++++uq++++++max+neval
##++is_inst("ggplot2")++336.845++386.660++459.243++431.710++483.474++867.637+++100
##+is_inst2("ggplot2")+1144.613+1276.847+1507.355+1410.054+1656.557+2747.508+++100|code-block|syntax|javascript|647054|entityMap^0|5|B|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|P|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|L|$]]

I suggest a more lightweight solution using <code>system.file</code>.

<pre><code>is_inst &lt;- function(pkg) {
 nzchar(system.file(package = pkg))
}

is_inst2 &lt;- function(pkg) {
 pkg %in% rownames(installed.packages())
}

library(microbenchmark)
microbenchmark(is_inst("aaa"), is_inst2("aaa"))
## Unit: microseconds
## expr min lq mean median uq max neval
## is_inst("aaa") 22.284 24.6335 42.84806 34.6815 47.566 252.568 100
## is_inst2("aaa") 1099.334 1220.5510 1778.57019 1401.5095 1829.973 17653.148 100
microbenchmark(is_inst("ggplot2"), is_inst2("ggplot2"))
## Unit: microseconds
## expr min lq mean median uq max neval
## is_inst("ggplot2") 336.845 386.660 459.243 431.710 483.474 867.637 100
## is_inst2("ggplot2") 1144.613 1276.847 1507.355 1410.054 1656.557 2747.508 100
</code></pre>

blocks|key|432658|text|还有CRAN包pacman，它具有p_load函数来安装一个或多个包(但仅在必要时)，然后加载它们。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|432659|entityMap|0|LINK|mutability|MUTABLE|url|http://cran.r-project.org/web/packages/pacman/vignettes/Introduction_to_pacman.html^0|H|6|7|6|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@$9|O|A|P|B|C]]|D|@$9|Q|A|R|1|S]]|E|$]]|$1|F|3|-4|5|6|7|T|8|@]|D|@]|E|$]]]|G|$H|$5|I|J|K|E|$L|M]]]]

There's also the CRAN package <a href="http://cran.r-project.org/web/packages/pacman/vignettes/Introduction_to_pacman.html">pacman</a> which has the <code>p_load</code> function to install one or more packages (but only if necessary) and then load them.

blocks|key|647065|text|requiredPackages+=+c('plyr','ggplot2','ggtern')
for(p+in+requiredPackages){
++if(!require(p,character.only+=+TRUE))+install.packages(p)
++library(p,character.only+=+TRUE)
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|647066|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>requiredPackages = c('plyr','ggplot2','ggtern')
for(p in requiredPackages){
 if(!require(p,character.only = TRUE)) install.packages(p)
 library(p,character.only = TRUE)
}
</code></pre>

blocks|key|646693|text|#+Function+to+check+whether+package+is+installed
++is.installed+<-+function(mypkg){
++++is.element(mypkg,+installed.packages()[,1])
++}+

++#+check+if+package+"hydroGOF"+is+installed
++if+(!is.installed("hydroGOF")){
++++install.packages("hydroGOF")
++}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|646694|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code># Function to check whether package is installed
 is.installed &lt;- function(mypkg){
 is.element(mypkg, installed.packages()[,1])
 } 

 # check if package "hydroGOF" is installed
 if (!is.installed("hydroGOF")){
 install.packages("hydroGOF")
 }
</code></pre>

blocks|key|646754|text|我在某个地方发现了一个packages脚本，我总是将它放在每个脚本中以加载我的库。它会做你所有的库处理(下载，安装和加载)，并且只在需要的时候。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|646755|#+Install+function+for+packages++++
packages<-function(x){
++x<-as.character(match.call()[[2]])
++if+(!require(x,character.only=TRUE)){
++++install.packages(pkgs=x,repos="http://cran.r-project.org")
++++require(x,character.only=TRUE)
++}
}
packages(ggplot2)
packages(reshape2)
packages(plyr)
#+etc+etc|code-block|syntax|javascript|646756|entityMap^0|B|8|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|P|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|L|$]]

I found a <code>packages</code> script somewhere that I always put in every script to load my libraries. It will do all your library handling (downloading, installing and loading), and only when needed. 

<pre><code># Install function for packages 
packages&lt;-function(x){
 x&lt;-as.character(match.call()[[2]])
 if (!require(x,character.only=TRUE)){
 install.packages(pkgs=x,repos="http://cran.r-project.org")
 require(x,character.only=TRUE)
 }
}
packages(ggplot2)
packages(reshape2)
packages(plyr)
# etc etc
</code></pre>

blocks|key|432592|text|我已经实现了静默安装和加载所需R包的功能。霍普或许能帮上忙。代码如下：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|432593|#+Function+to+Install+and+Load+R+Packages
Install_And_Load+<-+function(Required_Packages)
{
++++Remaining_Packages+<-+Required_Packages[!(Required_Packages+%25in%25+installed.packages()[,"Package"])];

++++if(length(Remaining_Packages))+
++++{
++++++++install.packages(Remaining_Packages);
++++}
++++for(package_name+in+Required_Packages)
++++{
++++++++library(package_name,character.only=TRUE,quietly=TRUE);
++++}
}

#+Specify+the+list+of+required+packages+to+be+installed+and+load++++
Required_Packages=c("ggplot2",+"Rcpp");

#+Call+the+Function
Install_And_Load(Required_Packages);|code-block|syntax|javascript|432594|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

I have implemented the function to install and load required R packages silently. Hope might help. Here is the code:

<pre><code># Function to Install and Load R Packages
Install_And_Load &lt;- function(Required_Packages)
{
 Remaining_Packages &lt;- Required_Packages[!(Required_Packages %in% installed.packages()[,"Package"])];

 if(length(Remaining_Packages)) 
 {
 install.packages(Remaining_Packages);
 }
 for(package_name in Required_Packages)
 {
 library(package_name,character.only=TRUE,quietly=TRUE);
 }
}

# Specify the list of required packages to be installed and load 
Required_Packages=c("ggplot2", "Rcpp");

# Call the Function
Install_And_Load(Required_Packages);
</code></pre>

blocks|key|646680|text|我使用的解决方案来自Sacha+Epskamp和Shuguang的输入。下面是函数：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|646681|instalaPacotes+<-+function(pacote)+{
++if+(!pacote+%25in%25+installed.packages())+install.packages(pacote)
}|code-block|syntax|javascript|646682|它以静默方式工作，如果已经安装了包"pacote“，则不会回显任何内容，否则会安装它。别忘了在两个引号之间写上包的名字！|646683|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

The solution I used derived from Sacha Epskamp and Shuguang's input. Here's the function:

<pre><code>instalaPacotes &lt;- function(pacote) {
 if (!pacote %in% installed.packages()) install.packages(pacote)
}
</code></pre>

It works silently, echoing nothing if package "pacote" is already installed and installing it otherwise. Don't forget to write the name of the package between quotes!

blocks|key|646730|text|试试这个怎么样？|type|unstyled|depth|inlineStyleRanges|entityRanges|data|646731|#will+install+the+pROC+library+if+you+don't+have+it
if(!is.element('pROC',+installed.packages()[,1]))
++{install.packages('pROC')
}else+{print("pROC+library+already+installed")}|code-block|syntax|javascript|646732|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

How about trying this? 

<pre><code>#will install the pROC library if you don't have it
if(!is.element('pROC', installed.packages()[,1]))
 {install.packages('pROC')
}else {print("pROC library already installed")}
</code></pre>

blocks|key|432097|text|为什么不直接从脚本中删除这一行？如果最终用户不具备按需安装xtable的智慧，那么您就会遇到更大的问题:-(+.也就是说，请查看installed.packages()|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|432098|编辑:见鬼，忍者快了一分钟！|432099|编辑:一个一般的建议:加载sos包，你会发现很容易得到很多“有做XXXXX的函数吗”问题的答案。|432100|entityMap^0|T|6|1S|K|0|0|D|3|0^^$0|@$1|2|3|4|5|6|7|L|8|@$9|M|A|N|B|C]|$9|O|A|P|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|Q|8|@]|D|@]|E|$]]|$1|H|3|I|5|6|7|R|8|@$9|S|A|T|B|C]]|D|@]|E|$]]|$1|J|3|-4|5|6|7|U|8|@]|D|@]|E|$]]]|K|$]]

Why not just delete the line from the script? If the end-user doesn't have the smarts to install <code>xtable</code> as needed, you've got bigger problems :-( .
That said, check out <code>installed.packages()</code> 

Edit: dang, Ninja'd by ONE minute!

Edit: a general suggestion: load the package <code>sos</code> , and you'll find it very easy to get answers to a lot of "is there a function that does XXXXX" questions.

blocks|key|432274|text|这个应该可以了。如果需要检查多个，可以将required.packages设置为向量。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|432275|required.packages+<-+"data.table"
new.packages+<-+required.packages[!(required.packages+%25in%25+installed.packages()[,"Package"])]
if(length(new.packages))+install.packages(new.packages)|code-block|syntax|javascript|432276|entityMap^0|K|H|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|P|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|L|$]]

This should do it. You can make <code>required.packages</code> a vector if you need to check for more than one.

<pre><code>required.packages &lt;- "data.table"
new.packages &lt;- required.packages[!(required.packages %in% installed.packages()[,"Package"])]
if(length(new.packages)) install.packages(new.packages)
</code></pre>

blocks|key|646789|text|阅读每个人的回复后，我随处可见一些提示，并创建了我自己的提示。但实际上和大多数都很相似。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|646790|##+These+codes+are+used+for+installing+packages
#+function+for+installing+needed+packages
installpkg+<-+function(x){
++++if(x+%25in%25+rownames(installed.packages())==FALSE)+{
++++++++if(x+%25in%25+rownames(available.packages())==FALSE)+{
++++++++++++paste(x,"is+not+a+valid+package+-+please+check+again...")
++++++++}+else+{
++++++++++++install.packages(x)+++++++++++
++++++++}

++++}+else+{
++++++++paste(x,"package+already+installed...")
++++}
}

#+install+necessary+packages
required_packages++<-+c("sqldf","car")
lapply(required_packages,installpkg)|code-block|syntax|javascript|646791|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Reading everyone's responses, I took some hints here and there and created mine. Actually very similar to most though.

<pre><code>## These codes are used for installing packages
# function for installing needed packages
installpkg &lt;- function(x){
 if(x %in% rownames(installed.packages())==FALSE) {
 if(x %in% rownames(available.packages())==FALSE) {
 paste(x,"is not a valid package - please check again...")
 } else {
 install.packages(x) 
 }

 } else {
 paste(x,"package already installed...")
 }
}

# install necessary packages
required_packages &lt;- c("sqldf","car")
lapply(required_packages,installpkg)
</code></pre>

blocks|key|646911|text|查看了我的旧函数，使用上面的提示更新了它，这就是我得到的结果。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|646912|#+VERSION+1.0
assign("installP",+function(pckgs){
++++ins+<-+function(pckg,+mc){
++++++++add+<-+paste(c("+",+rep("-",+mc%2B1-nchar(pckg)),+"+"),+collapse+=+"");
++++++++if(+!require(pckg,character.only=TRUE)+){
++++++++++++reps+<-+c("http://lib.stat.cmu.edu/R/CRAN","http://cran.uk.R-project.org");
++++++++++++for+(r+in+reps)+try(utils::install.packages(pckg,+repos=r),+silent=TRUE);
++++++++++++if(!require(pckg,character.only+=+TRUE)){+++cat("Package:+",pckg,add,"not+found.\n",sep="");
++++++++++++}else{++++++++++++++++++++++++++++++++++++++cat("Package:+",pckg,add,"installed.\n",sep="");}
++++++++}else{++++++++++++++++++++++++++++++++++++++++++cat("Package:+",pckg,add,"is+loaded.\n",sep="");+}+}
++++invisible(suppressMessages(suppressWarnings(lapply(pckgs,ins,+mc=max(nchar(pckgs))))));+cat("\n");+
},+envir=as.environment("dg_base"))

installP(c("base","a","TFX"))
Package:+base+-------------------+is+loaded.
Package:+a+----------------------+not+found.
Package:+TFX+--------------------+installed.|code-block|syntax|javascript|646913|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Looked at my old function, updated it using tips above and this is what i got.

<pre><code># VERSION 1.0
assign("installP", function(pckgs){
 ins &lt;- function(pckg, mc){
 add &lt;- paste(c(" ", rep("-", mc+1-nchar(pckg)), " "), collapse = "");
 if( !require(pckg,character.only=TRUE) ){
 reps &lt;- c("http://lib.stat.cmu.edu/R/CRAN","http://cran.uk.R-project.org");
 for (r in reps) try(utils::install.packages(pckg, repos=r), silent=TRUE);
 if(!require(pckg,character.only = TRUE)){ cat("Package: ",pckg,add,"not found.\n",sep="");
 }else{ cat("Package: ",pckg,add,"installed.\n",sep="");}
 }else{ cat("Package: ",pckg,add,"is loaded.\n",sep=""); } }
 invisible(suppressMessages(suppressWarnings(lapply(pckgs,ins, mc=max(nchar(pckgs)))))); cat("\n"); 
}, envir=as.environment("dg_base"))

installP(c("base","a","TFX"))
Package: base ------------------- is loaded.
Package: a ---------------------- not found.
Package: TFX -------------------- installed.
</code></pre>

I have an R script that is shared with several users on different computers. One of its lines contains the <code>install.packages("xtable")</code> command.

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).

How can I make first check if the packages are installed and then only run <code>install.packages()</code> for the ones that are not?

Check for installed packages before running install.packages()

我有一个与不同计算机上的多个用户共享的R脚本。它的一行包含install.packages("xtable")命令。问题是，每次有人运行脚本时，R显然会花费大量时间重新安装包(实际上需要花费一些时间，因为实际情况下有几个包的向量)。如何才能先检查软件包是否已安装，然后只对未安装的软件包运行install.packages()？

问在运行install.packages()之前检查已安装的软件包
EN

回答 15

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问在运行install.packages()之前检查已安装的软件包EN

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问在运行install.packages()之前检查已安装的软件包
EN