使用dplyr查找重复的元素 [英] Find duplicated elements with dplyr

问题描述

我尝试使用提供的代码此处使用dplyr查找所有重复的元素，例如：

I tried using the code presented here to find ALL duplicated elements with dplyr like this:

library(dplyr)

mtcars %>%
mutate(cyl.dup = cyl[duplicated(cyl) | duplicated(cyl, from.last = TRUE)])

如何转换在这里查找dplyr的所有重复元素？我上面的代码只是抛出错误？甚至更好的是，还有另一个函数比卷积 x [duplicated（x）|

How can I convert code presented here to find ALL duplicated elements with dplyr? My code above just throws an error? Or even better, is there another function that will achieve this more succinctly than the convoluted x[duplicated(x) | duplicated(x, from.last = TRUE)]) approach?

推荐答案

我猜想你可能会重复（x，from.last = TRUE）]）方法？为此，请使用过滤器：

I guess you could use filter for this purpose:

mtcars %>% 
  group_by(carb) %>% 
  filter(n()>1)

小示例（请注意，我添加了 summarize（）以证明结果数据集不包含重复的'carb'行。我使用了'carb'而不是' cyl，因为 carb具有唯一值，而 cyl则没有）：

Small example (note that I added summarize() to prove that the resulting data set does not contain rows with duplicate 'carb'. I used 'carb' instead of 'cyl' because 'carb' has unique values whereas 'cyl' does not):

mtcars %>% group_by(carb) %>% summarize(n=n())
#Source: local data frame [6 x 2]
#
#  carb  n
#1    1  7
#2    2 10
#3    3  3
#4    4 10
#5    6  1
#6    8  1

mtcars %>% group_by(carb) %>% filter(n()>1) %>% summarize(n=n())
#Source: local data frame [4 x 2]
#
#  carb  n
#1    1  7
#2    2 10
#3    3  3
#4    4 10

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