根据指定所需顺序的目标向量订购数据帧行 [英] Order data frame rows according to a target vector that specifies the desired order

问题描述

有没有更简单的方法来确保数据框的行按照目标向量排序，就像我在下面的简短示例中实现的一样？

Is there an easier way to ensure that a data frame's rows are ordered according to a "target" vector as the one I implemented in the short example below?

df <- data.frame(name = letters[1:4], value = c(rep(TRUE, 2), rep(FALSE, 2)))

df
#   name value
# 1    a  TRUE
# 2    b  TRUE
# 3    c FALSE
# 4    d FALSE

target <- c("b", "c", "a", "d")

这似乎有点太复杂了，以完成工作：

This somehow seems to be a bit too "complicated" to get the job done:

idx <- sapply(target, function(x) {
    which(df$name == x)
})
df <- df[idx,]
rownames(df) <- NULL

df 
#   name value
# 1    b  TRUE
# 2    c FALSE
# 3    a  TRUE
# 4    d FALSE

推荐答案

尝试 match ：

df <- data.frame(name=letters[1:4], value=c(rep(TRUE, 2), rep(FALSE, 2)))
target <- c("b", "c", "a", "d")
df[match(target, df$name),]

  name value
2    b  TRUE
3    c FALSE
1    a  TRUE
4    d FALSE

只要您的目标包含与 df $ name 完全相同的元素，它将工作，并且不包含重复的值。

It will work as long as your target contains exactly the same elements as df$name, and neither contain duplicate values.

从匹配：

match returns a vector of the positions of (first) matches of its first argument 
in its second.

因此 match 找到匹配的行号 target 的元素，然后按照该顺序返回 df 。

Therefore match finds the row numbers that matches target's elements, and then we return df in that order.

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