如何实现在数据框中显示的最重复的值或名称

Question

我有一个与R中的库dplyr相关的简单问题。

我的实际数据框如下所示：

Players <- data.frame(Group = c("A", "A", "A", "A", "B", "B", "B", "C","C","C"), Players= c("Jhon", "Jhon", "Jhon", "Charles", "Mike", "Mike","Carl", "Max", "Max","Max"))

:

   Group Players
      A    Jhon
      A    Jhon
      A    Jhon
      A  Charles
      B    Mike
      B    Mike
      B    Carl
      C     Max
      C     Max
      C     Max

我希望获得另一个数据框，让每个组的玩家重复多次以及列出多少次。所以我想得到这个数据框：

Group Players TimesListed

A    Jhon      3
B    Mike      2
B    Max       3

我试过这个：

    Station <- Players %>% group_by(Group,Players) %>% 
        summarise(TimesListed=length(Players)) %>% 
        summarise(TimesListed=max(TimesListed))

但是我得到的数据框没有像这样的玩家的名字：

   Group TimesListed

1      A           3
2      B           2
3      C           3

任何的想法？谢谢！

Answer 1

这应该可以满足您的需求：

library(dplyr)

Players %>% 
  group_by(Group) %>% 
  count(Players) %>% 
  top_n(1, n)

# A tibble: 3 x 3
# Groups:   Group [3]
   Group Players     n
  <fctr>  <fctr> <int>
1      A    Jhon     3
2      B    Mike     2
3      C     Max     3

您可以执行以下操作将因子转换为字符：

Players[] <- lapply(Players, as.character)

如果您需要将变量n更改为TimesListed，请将以下内容添加到链的末尾：

rename(TimesListed = n)

Answer 2

您可以在基础R中使用aggregate函数：

aggregate(.~Group,dat,function(x)max(table(x)))
  Group Players
1     A       3
2     B       2
3     C       3

Answer 3

为了完整起见，这是使用data.table的解决方案。

library(data.table)

setDT(Players)

Players[, .(TimesListed = .N), by = .(Group, Players)][
  , .SD[which.max(TimesListed)], by = Group]
#    Group Players TimesListed
# 1:     A    Jhon           3
# 2:     B    Mike           2
# 3:     C     Max           3

上面的解决方案将返回TimesListed中最大的第一行。如果我们想要返回所有等于最大值的行，我们可以执行以下操作。在这种情况下，两种解决方案会产生相同的结果。

Players[, .(TimesListed = .N), by = .(Group, Players)][
  , .SD[TimesListed == max(TimesListed)], by = Group]
#    Group Players TimesListed
# 1:     A    Jhon           3
# 2:     B    Mike           2
# 3:     C     Max           3