小编jgi*_*gan的帖子

当我尝试调用install_github时,我收到以下错误(不仅是这个包,而是所有github包):

> install_github('ramnathv/slidify')
Downloading github repo ramnathv/slidify@master
Error in curl::curl_fetch_memory(url, handle = handle) :
Problem with the SSL CA cert (path? access rights?)

但是,如果我直接使用RCurl来访问带有ssl的github,我不会遇到任何问题:

>  x <- getBinaryURL(
          url='https://github.com/ramnathv/slidify/archive/master.zip',
          followlocation=1L
          )

无错误地工作,因此RCurl可以正确验证SSL证书并下载存档文件.

> sessionInfo()
R version 3.2.1 (2015-06-18)
Platform: x86_64-pc-linux-gnu (64-bit)
Running under: Debian GNU/Linux 8 (jessie)

locale:
 [1] LC_CTYPE=en_US.utf8       LC_NUMERIC=C             
 [3] LC_TIME=en_US.utf8        LC_COLLATE=en_US.utf8    
 [5] LC_MONETARY=en_US.utf8    LC_MESSAGES=en_US.utf8   
 [7] LC_PAPER=en_US.utf8       LC_NAME=C                
 [9] LC_ADDRESS=C              LC_TELEPHONE=C           
 [11] LC_MEASUREMENT=en_US.utf8 LC_IDENTIFICATION=C      

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

other attached packages: …

考虑以下:

library(tidyverse)

df <- tibble(x = rnorm(100), y = rnorm(100, 10, 2), z = x * y)

df %>% 
mutate_all(funs(avg = mean(.), dev = sd(.), scaled = (. - mean(.)) / sd(.)))

有没有办法通过引用和列来避免调用mean和sd两次.我想到的是类似的东西avgdev

df %>% 
mutate_all(funs(avg = mean(.), dev = sd(.), scaled = (. - avg) / dev))

显然,这是行不通的,因为没有列avg和dev,但是x_avg,x_dev,y_avg,y_dev,等.

有一个好办法,内部funs使用rlang的工具以编程方式创建这些列引用,这样我可以参考由以前命名的参数创建的列funs(当.是x,我将引用x_mean和 …