我尝试运行以下代码,但每次都会出现如下错误:Error in eval(expr, envir, enclos) : could not find function "."
。如何解决?有人能帮忙吗?
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)
]
以下是会话信息
> 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
sessionInfo()
。 - user3710546data.table_1.9.2
版本中,而在data.table_1.9.4
版本中则没有出现。 - user3710546install.packages("data.table", type="source", dependencies=TRUE)
,然后按照此顺序使用unloadNamespace
命令卸载 'data.table'、'reshape2' 和 'plyr' 包后,我能够加载1.9.4版本并运行该代码。 - IRTFM