我试图将我对plyr的理解转化为dplyr,但我不知道如何按多个列进行分组.
# make data with weird column names that can't be hard coded
data = data.frame(
asihckhdoydkhxiydfgfTgdsx = sample(LETTERS[1:3], 100, replace=TRUE),
a30mvxigxkghc5cdsvxvyv0ja = sample(LETTERS[1:3], 100, replace=TRUE),
value = rnorm(100)
)
# get the columns we want to average within
columns = names(data)[-3]
# plyr - works
ddply(data, columns, summarize, value=mean(value))
# dplyr - raises error
data %.%
group_by(columns) %.%
summarise(Value = mean(value))
#> Error in eval(expr, envir, enclos) : index out of bounds
将plyr示例翻译成dplyr式语法,我遗漏了什么?
Edit 2017:Dplyr已经更新,因此有了更简单的解决方案.查看当前 Select 的答案.