将一组按手段添加到原始数据 [英] Adding a column of means by group to original data

问题描述

我想根据 R data.frame 中的因子列添加一列手段。像这样：

I want to add a column of means based on factor column in R data.frame. Like this:

df1 <- data.frame(X = rep(x = LETTERS[1:2], each = 3), Y = 1:6)
df2 <- aggregate(data = df1, Y ~ X, FUN = mean)
df3 <- merge(x = df1, y = df2, by = "X", suffixes = c(".Old",".New"))
df3
#   X Y.Old Y.New
# 1 A     1     2
# 2 A     2     2
# 3 A     3     2
# 4 B     4     5
# 5 B     5     5
# 6 B     6     5

要完成此问题，我必须创建两个不必要的 data.frames 。我想知道一种方法，通过因子列附加一列手段到我原来的 data.frame 中，而不创建任何额外的 data.frames 。感谢您的时间和帮助。

To accomplish this problem I've to create two unnecessary data.frames. I'd like to know a way to append a column of means by factor column into my original data.frame without creating any extra data.frames. Thanks for your time and help.

推荐答案

这是 ave 功能用于。

df1$Y.New <- ave(df1$Y, df1$X)

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