Question

注意：此问题的标题已经过编辑，使其成为plyr函数屏蔽其dplyr对应项时问题的规范问题。问题的其余部分保持不变。

假设我有以下数据：

dfx <- data.frame(
  group = c(rep('A', 8), rep('B', 15), rep('C', 6)),
  sex = sample(c("M", "F"), size = 29, replace = TRUE),
  age = runif(n = 29, min = 18, max = 54)
)

使用旧的plyr我可以使用以下代码创建一个汇总我的数据的小表：

require(plyr)
ddply(dfx, .(group, sex), summarize,
      mean = round(mean(age), 2),
      sd = round(sd(age), 2))

输出如下：

  group sex  mean    sd
1     A   F 49.68  5.68
2     A   M 32.21  6.27
3     B   F 31.87  9.80
4     B   M 37.54  9.73
5     C   F 40.61 15.21
6     C   M 36.33 11.33

我正在尝试将代码移至dplyr和%>%运算符。我的代码采用DF然后按组和性别对其进行分组，然后对其进行汇总。那就是：

dfx %>% group_by(group, sex) %>% 
  summarise(mean = round(mean(age), 2), sd = round(sd(age), 2))

但我的输出是：

  mean   sd
1 35.56 9.92

我做错了什么？

Answer 1

这里的问题是你首先加载dplyr然后plyr，所以plyr的函数summarise掩盖了dplyr的函数summarise。当发生这种情况时，您会收到此警告：

require(plyr)
    Loading required package: plyr
------------------------------------------------------------------------------------------
You have loaded plyr after dplyr - this is likely to cause problems.
If you need functions from both plyr and dplyr, please load plyr first, then dplyr:
library(plyr); library(dplyr)
------------------------------------------------------------------------------------------

Attaching package: ‘plyr’

The following objects are masked from ‘package:dplyr’:

    arrange, desc, failwith, id, mutate, summarise, summarize

因此，为了使您的代码正常工作，请分离plyr detach(package:plyr)或重新启动R并先加载plyr然后再加载dplyr（或仅加载dplyr）：

library(dplyr)
dfx %>% group_by(group, sex) %>% 
  summarise(mean = round(mean(age), 2), sd = round(sd(age), 2))
Source: local data frame [6 x 4]
Groups: group

  group sex  mean    sd
1     A   F 41.51  8.24
2     A   M 32.23 11.85
3     B   F 38.79 11.93
4     B   M 31.00  7.92
5     C   F 24.97  7.46
6     C   M 36.17  9.11

或者您可以在代码中明确调用dplyr的汇总，因此无论您如何加载包，都会调用正确的函数：

dfx %>% group_by(group, sex) %>% 
  dplyr::summarise(mean = round(mean(age), 2), sd = round(sd(age), 2))

Answer 2

您的代码正在调用plyr::summarise而不是dplyr::summarise，因为您已加载的顺序＆＃34; plyr＆＃34;和＆＃34; dplyr＆＃34;。

演示：

library(dplyr) ## I'm guessing this is the order you loaded
library(plyr)
dfx %>% group_by(group, sex) %>% 
  summarise(mean = round(mean(age), 2), sd = round(sd(age), 2))
#    mean   sd
# 1 36.88 9.76
dfx %>% group_by(group, sex) %>% 
  dplyr::summarise(mean = round(mean(age), 2), sd = round(sd(age), 2))
# Source: local data frame [6 x 4]
# Groups: group
# 
#   group sex  mean    sd
# 1     A   F 32.17  6.30
# 2     A   M 30.98  7.37
# 3     B   F 38.20  7.67
# 4     B   M 33.12 12.24
# 5     C   F 43.91 10.31
# 6     C   M 47.53  8.25

当我在`dplyr`之后加载`plyr`时，为什么汇总或变异不能用于group_by？

2 个答案: