根据具有特定顺序的向量对数据框行进行排序 [英] Order data frame rows according to vector with specific order

问题描述

是否有更简单的方法来确保数据框的行根据目标"向量进行排序，就像我在下面的简短示例中实现的那样?

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"而无法完成工作:

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

Try 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 target 包含与 df$name 完全相同的元素，并且都不包含重复值，它就会工作.

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

来自?match:

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

因此match找到与target的元素匹配的行号，然后我们按照这个顺序返回df.

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

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