使用以下示例数据帧:
a <- c(1:5)
b <- c("Cat", "Dog", "Rabbit", "Cat", "Dog")
c <- c("Dog", "Rabbit", "Cat", "Dog", "Dog")
d <- c("Rabbit", "Cat", "Dog", "Dog", "Rabbit")
e <- c("Cat", "Dog", "Dog", "Rabbit", "Cat")
f <- c("Cat", "Dog", "Dog", "Rabbit", "Cat")
df <- data.frame(a,b,c,d,e,f)
我想研究如何在不必输入所有列名的情况下对列进行重新排序，例如df[,c("a","d","e","f","b","c")]
我怎么说我想要f列之后的b列和c列呢？(仅引用要移动的列或列范围？).
非常感谢您的帮助.
如果只是将某些列移到末尾，可以创建一个小助手函数，如下所示:
movetolast <- function(data, move) {
data[c(setdiff(names(data), move), move)]
}
movetolast(df, c("b", "c"))
# a d e f b c
# 1 1 Rabbit Cat Cat Cat Dog
# 2 2 Cat Dog Dog Dog Rabbit
# 3 3 Dog Dog Dog Rabbit Cat
# 4 4 Dog Rabbit Rabbit Cat Dog
# 5 5 Rabbit Cat Cat Dog Dog
我建议大家养成使用列位置的习惯，尤其不是从程序的Angular ，因为这些位置可能会改变.
下面是对上述函数的扩展解释.它允许您将列移动到第一个或最后一个位置，或在另一列之前或之后.
moveMe <- function(data, tomove, where = "last", ba = NULL) {
temp <- setdiff(names(data), tomove)
x <- switch(
where,
first = data[c(tomove, temp)],
last = data[c(temp, tomove)],
before = {
if (is.null(ba)) stop("must specify ba column")
if (length(ba) > 1) stop("ba must be a single character string")
data[append(temp, values = tomove, after = (match(ba, temp)-1))]
},
after = {
if (is.null(ba)) stop("must specify ba column")
if (length(ba) > 1) stop("ba must be a single character string")
data[append(temp, values = tomove, after = (match(ba, temp)))]
})
x
}
try 以下方法.
moveMe(df, c("b", "c"))
moveMe(df, c("b", "c"), "first")
moveMe(df, c("b", "c"), "before", "e")
moveMe(df, c("b", "c"), "after", "e")
您需要调整它以进行一些错误判断——例如，如果您try 将列"b"和"c"移动到"c"之前，您(显然)会得到一个错误.