Question

library(magrittr) 

myDf <- dataSetSubsetting 
        %>% !is.na(.[,c("colx")]) 
        %>% !is.na(.[,c("coly")])
        %>% someFunction(.[,c("colx", "coly")], .)

我认为magrittr的工作原理。但是，它给我一个错误：

384: myDf <- dataSetSubsetting %>% !is.na(.[,c("colx")])
385: %>%
     ^

为什么？！

Answer 1

以下是基于erasmortg评论的更详细解释。

library(dplyr)

#* Works
mtcars %>%
  mutate(am = factor(am, 0:1, c("Automatic", "Manual")))

#* Fails: the interpreter looks at the end of the first 
#*        line and sees no operator, so it prints 'mtcars'
#*        and declares the operation complete.
#*        It then looks at the second line and can't find
#*        the left hand side for '%>%', causing an error.
mtcars
  %>% mutate(am = factor(am, 0:1, c("Automatic", "Manual")))

#* Fails: Similar story to the previous example.  In this case,
#*        printing is delayed until all of the statements within
#*        the braces successfully run.
{mtcars
  %>% mutate(am = factor(am, 0:1, c("Automatic", "Manual")))}

#* Succeeds: The interpreter sees that you've opened
#*    with parentheses, and tries to connect all of the
#*    lines into a coherent statement.  With the parentheses,
#*    when the interpreter sees no operator at the end of 
#*    'mtcars', it says to itself, "I hope I find one on the 
#*    next line" and tries to piece it together.
(mtcars
  %>% mutate(am = factor(am, 0:1, c("Automatic", "Manual"))))

％＆gt;％运算符R产生意外错误

1 个答案: