dplyr非常快,但我想知道我是否遗漏了一些东西:是否有可能总结出几个变量.例如:
library(dplyr)
library(reshape2)
(df=dput(structure(list(sex = structure(c(1L, 1L, 2L, 2L), .Label = c("boy",
"girl"), class = "factor"), age = c(52L, 58L, 40L, 62L), bmi = c(25L,
23L, 30L, 26L), chol = c(187L, 220L, 190L, 204L)), .Names = c("sex",
"age", "bmi", "chol"), row.names = c(NA, -4L), class = "data.frame")))
sex age bmi chol
1 boy 52 25 187
2 boy 58 23 220
3 girl 40 30 190
4 girl 62 26 204
dg=group_by(df,sex)
使用这个小型数据帧,它很容易编写
summarise(dg,mean(age),mean(bmi),mean(chol))
而且我知道,为了得到我想要的东西,我可以融化,获得手段,然后如dcast
dm=melt(df, id.var='sex')
dmg=group_by(dm, sex, variable); …我想dplyr::group_by在另一个函数中使用函数,但我不知道如何将参数传递给这个函数.
有人能提供一个有效的例子吗？
library(dplyr)
data(iris)
iris %.% group_by(Species) %.% summarise(n = n()) #
## Source: local data frame [3 x 2]
## Species n
## 1 virginica 50
## 2 versicolor 50
## 3 setosa 50
mytable0 <- function(x, ...) x %.% group_by(...) %.% summarise(n = n())
mytable0(iris, "Species") # OK
## Source: local data frame [3 x 2]
## Species n
## 1 virginica 50
## 2 versicolor 50
## 3 setosa 50
mytable1 <- function(x, key) x …