如何使用赋值运算符结束管道？

I want to end a pipe with an assignment operator in R.

我想在R中使用赋值运算符结束管道。

my goal (in pseudo R):

我的目标（在伪R中）：

data %>% analysis functions %>% analyzedData

where data and analyzedData are both a data.frame.

其中data和analyzeData都是data.frame。

I've tried a few variants of this, each giving a unique error message. some iterations I've tried:

我尝试了一些这方面的变种，每个都给出了一个独特的错误信息。我试过的一些迭代：

data %>% analysis functions %>% -> analyzedData
data %>% analysis functions %>% .-> analyzedData
data %>% analysis functions %>% <-. analyzedData
data %>% analysis functions %>% <- analyzedData

Error messages:

错误消息：

Error in function_list[[k]](value) : 
  could not find function "analyzedData"
Error: object 'analyzedData' not found
Error: unexpected assignment in: ..

Update: the way I figured out to do this is:

更新：我想出这样做的方式是：

data %>% do analysis %>% {.} -> analyzedData

This way, to troubleshoot / debug a long pipe, you can drop these two line into your pipe to minimize code rerun and to isolate the problem.

这样，要对长管道进行故障排除/调试，可以将这两行放入管道中，以最大限度地减少代码重新运行并隔离问题。

data %>% pipeline functions %>% 
   {.}-> tempWayPoint
   tmpWayPoint %>% 
more pipeline functions %>% {.} -> endPipe 

4 个解决方案

#1

It's probably easiest to do the assignment as the first thing (like scoa mentions) but if you really want to put it at the end you could use assign

作为第一件事（如scoa提及），这可能是最简单的做法，但如果你真的想把它放在最后，你可以使用assign

mtcars %>% 
  group_by(cyl) %>% 
  summarize(m = mean(hp)) %>% 
  assign("bar", .)

which will store the output into "bar"

将输出存储到“bar”

Alternatively you could just use the -> operator. You mention it in your question but it looks like you use something like

或者你可以使用 - >运算符。你在问题中提到它，但看起来你喜欢使用类似的东西

mtcars %>% -> yourvariable

instead of

代替

mtcars -> yourvariable

You don't want to have %>% in front of the ->

您不希望在 - >前面有％>％

#2

It looks like you're trying to decorate the %>% pipeline operator with the side-effect of creating a new object. One would assume that you could use the assignment operator -> for this, but it won't work in a pipeline. This is because -> has lower precedence than user-defined operators like %>%, which messes up the parsing: your pipeline will be parsed as (initial_stages) -> (final_stages) which is nonsensical.

看起来您正在尝试使用创建新对象的副作用来装饰％>％管道运算符。可以假设你可以使用赋值运算符 - >为此，但它不能在管道中工作。这是因为 - >的优先级低于用户定义的运算符，如％>％，这会影响解析：您的管道将被解析为（initial_stages） - >（final_stages），这是无意义的。

A solution is to replace -> with a user-defined version. While we're at it, we might as well use the lazyeval package, to ensure it will create the object where it's supposed to go:

解决方案是用用户定义的版本替换 - >。虽然我们正在使用它，但我们不妨使用lazyeval包，以确保它将创建它应该去的对象：

`%->%` <- function(value, x)
{
    x <- lazyeval::lazy(x)
    assign(deparse(x$expr), value, x$env)
    value
}

An example of this in use:

使用中的一个例子：

smry <- mtcars %>% 
    group_by(cyl) %->%   # ->, not >
    tmp %>%
    summarise(m=mean(mpg))

tmp
#Source: local data frame [32 x 11]
#Groups: cyl
#
#    mpg cyl  disp  hp drat    wt  qsec vs am gear carb
#1  21.0   6 160.0 110 3.90 2.620 16.46  0  1    4    4
#2  21.0   6 160.0 110 3.90 2.875 17.02  0  1    4    4
#3  22.8   4 108.0  93 3.85 2.320 18.61  1  1    4    1
#4  21.4   6 258.0 110 3.08 3.215 19.44  1  0    3    1
#5  18.7   8 360.0 175 3.15 3.440 17.02  0  0    3    2
#..  ... ...   ... ...  ...   ...   ... .. ..  ...  ...

smry
#Source: local data frame [3 x 2]
#
#  cyl        m
#1   4 26.66364
#2   6 19.74286
#3   8 15.10000

#3

You can think of a pipe chain as a multiline function, that works as every other multiline function. The usual way to save the output is to assign it on the first line :

您可以将管道链视为多线功能，与其他所有多线功能一样。保存输出的常用方法是在第一行分配它：

analyzedData <- data %>% analysis functions

Like you would do :

就像你会做的那样：

plot <- ggplot(data,aes(x=x,y=x)) +
  geom_point()

#4

Update: the way I figured out to do this is: data %>% do analysis %>% {.} -> analyzedData

更新：我想出的方法是：数据％>％做分析％>％{。} - > analyzeData

This way, to troubleshoot / debug a long pipe, you can drop these two line into your pipe to minimize code rerun and to isolate the problem.

这样，要对长管道进行故障排除/调试，可以将这两行放入管道中，以最大限度地减少代码重新运行并隔离问题。

data %>% pipeline functions %>% 
   {.}-> tempWayPoint
   tmpWayPoint %>% 
more pipeline functions %>% {.} -> endPipe 

If you have a better way of doing this please let me know.

如果您有更好的方法，请告诉我。