数据表错误找不到函数“." [英] Data table error could not find function "."

问题描述

我正在尝试运行以下代码.每当我尝试运行代码时，都会出现以下错误:Error in eval(expr, envir, enclos) : could not find function "."我该如何解决?有人可以帮忙吗?

I am trying to run the following piece of code. Whenever I try to run the code I get the following error: Error in eval(expr, envir, enclos) : could not find function "." How can I fix it? Could someone help?

data(mtcars)
library(data.table)
mtcarsDT <- data.table(mtcars)
mtcarsDT[ mpg > 20,
        .(AvgHP = mean(hp),
        "MinWT(kg)" = min(wt * 453.6)), # wt lbs
        by = .(cyl, under5gears = gear < 5)
        ]

这是会话信息

> sessionInfo()
R version 3.1.2 (2014-10-31)
Platform: x86_64-apple-darwin10.8.0 (64-bit)

locale:
[1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
[1] data.table_1.9.2

loaded via a namespace (and not attached):
[1] digest_0.6.8    htmltools_0.2.6 plyr_1.8.1      Rcpp_0.11.3     reshape2_1.4.1  rmarkdown_0.3.3 stringr_0.6.2  
[8] tools_3.1.2 

推荐答案

显然我在 2.5 年前提供的说明仍然适用于使用过时版本的 Mac R 的人.假设你有 Xcode 和命令行工具安装后，您需要首先 a) 重新启动 R(不加载任何版本的 data.table.、reshape2 和 dplyr)，或 b) 删除任何可能与测试加载新包的能力冲突的已加载命名空间:

Apparently the instructions I offered 2.5 years ago are still current for people using out-of-date versions of Mac R. Assuming you have Xcode and the Command Line Tools installed, you need to first either a) restart R (without loading any of the versions of data.table., reshape2, and dplyr), or b) remove any loaded Namespaces that might conflict with the ability to test-load the new packages:

unloadNamespace('data.table')
unloadNamespace('reshape2')
unloadNamespace('plyr')

然后从源代码构建:

install.packages("data.table", type="source", dependencies=TRUE)

在安装二进制包时从源代码构建可能会起作用的原因可能是前一种策略可以让您更好地检查版本依赖关系.

The reason that building from source might work when installing a binary package might not is that the former strategy gets you better checking for version dependencies.

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