我有一个数据框，其中包含列a、b和c。我想在b和c之间添加一个新的列d。
我知道可以使用cbind将d添加到末尾，但如何在两列之间插入它呢？
18个回答
116
我建议你使用tibble包中的add_column()函数。
library(tibble)
dataset <- data.frame(a = 1:5, b = 2:6, c=3:7)
add_column(dataset, d = 4:8, .after = 2)
请注意，您可以使用列名代替列索引：
add_column(dataset, d = 4:8, .after = "b")
如果更方便的话，可以使用参数.before而不是.after。
add_column(dataset, d = 4:8, .before = "c")
- Kevin Zarca
1
55
在您的新列中添加：
df$d <- list/data
然后您可以重新排列它们。
df <- df[, c("a", "b", "d", "c")]
- ashah57
2
1我发现在使用
setcolorder时，结合列号（而不是列名）进行重新排序也非常有用，因为一旦列数变得非常大，你就可以开始使用seq和rep来完成大部分工作。此外，还可以使用算术运算符。例如：setcolorder(data, c(1, (num_cols -2), (num_cols -1), num_cols, seq(from = 2, to = (num_cols - 3))))。 - n1k31t43我应该提醒一下，
setcolorder 是针对 data.table 而不是 data.frame 的！ - n1k31t426
您可以使用[,]重新排序列，或按您想要的顺序呈现列。
d <- data.frame(a=1:4, b=5:8, c=9:12)
target <- which(names(d) == 'b')[1]
cbind(d[,1:target,drop=F], data.frame(d=12:15), d[,(target+1):length(d),drop=F])
a b d c
1 1 5 12 9
2 2 6 13 10
3 3 7 14 11
4 4 8 15 12
- Matthew Lundberg
2
17这是一个很好的回答。但我不得不承认，这也是为什么R对于初学者来说可能很困难的一个很好的例子。 - tumultous_rooster
4话虽如此，我认为@ashah57在下面给出了一个更简单、更清晰的答案。在这种情况下，不需要过于花哨。 - tumultous_rooster
18
假设b总是紧随着c，这段代码将在b后面添加一列，无论b在数据框中的位置如何。
> test <- data.frame(a=1,b=1,c=1)
> test
a b c
1 1 1 1
> bspot <- which(names(test)=="b")
> data.frame(test[1:bspot],d=2,test[(bspot+1):ncol(test)])
a b d c
1 1 1 2 1
或者更自然地说：
data.frame(append(test, list(d=2), after=match("b", names(test))))
- thelatemail
9
创建一个示例数据框并向其中添加一列。
结果是：
df = data.frame(a = seq(1, 3), b = seq(4,6), c = seq(7,9))
df['d'] <- seq(10,12)
df
a b c d
1 1 4 7 10
2 2 5 8 11
3 3 6 9 12
按列索引重新排列
df[, colnames(df)[c(1:2,4,3)]]
或者按列名排序
df[, c('a', 'b', 'd', 'c')]
结果是：
a b d c
1 1 4 10 7
2 2 5 11 8
3 3 6 12 9
- buhtz
5
这里有一个快速而简单的方法在数据框中的特定位置插入一列。在我的案例中，原始数据框有5列：
1）首先，让我们创建测试数据框：
c1、c2、c3、c4、c5，我将在c2和c3之间插入新列c2b。1）首先，让我们创建测试数据框：
> dataset <- data.frame(c1 = 1:5, c2 = 2:6, c3=3:7, c4=4:8, c5=5:9)
> dataset
c1 c2 c3 c4 c5
1 1 2 3 4 5
2 2 3 4 5 6
3 3 4 5 6 7
4 4 5 6 7 8
5 5 6 7 8 9
2) 在我们的数据框中添加新列c2b：
> dataset$c2b <- 10:14
> dataset
c1 c2 c3 c4 c5 c2b
1 1 2 3 4 5 10
2 2 3 4 5 6 11
3 3 4 5 6 7 12
4 4 5 6 7 8 13
5 5 6 7 8 9 14
3) 基于列索引重新排序数据框。在我的情况下，我想在现有的第2列和第3列之间插入新的第6列。我通过使用向量c（1:2, 6, 3:5）来定位我的数据框上的列，这等同于c（1, 2, 6, 3, 4, 5）。
> dataset <- dataset[,c(1:2, 6, 3:5)]
> dataset
c1 c2 c2b c3 c4 c5
1 1 2 10 3 4 5
2 2 3 11 4 5 6
3 3 4 12 5 6 7
4 4 5 13 6 7 8
5 5 6 14 7 8 9
在这里！
- Ricardo
4
你想要在由列 x 和 y 定义的旧数据框(old.df)中添加列 z。
z = rbinom(1000, 5, 0.25)
old.df <- data.frame(x = c(1:1000), y = rnorm(1:1000))
head(old.df)
定义一个新的数据框，称为new.df。
new.df <- data.frame(x = old.df[,1], z, y = old.df[,2])
head(new.df)
- marbel
4
简单解决方案。在一个有5列的数据框中，如果你想在第3列和第4列之间插入另一列...
tmp <- data[, 1:3]
tmp$example <- NA # or any value.
data <- cbind(tmp, data[, 4:5]
- Jose Luis Camps
2
就算只是一点点价值，我也写了一个函数来完成这个任务：
[已删除]
现在我已经更新了这个函数，增加了before和after功能，并将place默认设置为1。它还兼容数据表格：
#####
# FUNCTION: InsertDFCol(colName, colData, data, place = 1, before, after)
# DESCRIPTION: Takes in a data, a vector of data, a name for that vector and a place to insert this vector into
# the data frame as a new column. If you put place = 3, the new column will be in the 3rd position and push the current
# 3rd column up one (and each subsuquent column up one). All arguments must be set. Adding a before and after
# argument that will allow the user to say where to add the new column, before or after a particular column.
# Please note that if before or after is input, it WILL override the place argument if place is given as well. Also, place
# defaults to adding the new column to the front.
#####
InsertDFCol <- function(colName, colData, data, place = 1, before, after) {
# A check on the place argument.
if (length(names(data)) < place) stop("The place argument exceeds the number of columns in the data for the InsertDFCol function. Please check your place number")
if (place <= 0 & (!missing(before) | !(missing(after)))) stop("You cannot put a column into the 0th or less than 0th position. Check your place argument.")
if (place %% 1 != 0 & (!missing(before) | !(missing(after)))) stop("Your place value was not an integer.")
if (!(missing(before)) & !missing(after)) stop("You cannot designate a before AND an after argument in the same function call. Please use only one or the other.")
# Data Table compatability.
dClass <- class(data)
data <- as.data.frame(data)
# Creating booleans to define whether before or after is given.
useBefore <- !missing(before)
useAfter <- !missing(after)
# If either of these are true, then we are using the before or after argument, run the following code.
if (useBefore | useAfter) {
# Checking the before/after argument if given. Also adding regular expressions.
if (useBefore) { CheckChoice(before, names(data)) ; before <- paste0("^", before, "$") }
if (useAfter) { CheckChoice(after, names(data)) ; after <- paste0("^", after, "$") }
# If before or after is given, replace "place" with the appropriate number.
if (useBefore) { newPlace <- grep(before, names(data)) ; if (length(newPlace) > 1) { stop("Your before argument matched with more than one column name. Do you have duplicate column names?!") }}
if (useAfter) { newPlace <- grep(after, names(data)) ; if (length(newPlace) > 1) { stop("Your after argument matched with more than one column name. Do you have duplicate column names?!") }}
if (useBefore) place <- newPlace # Overriding place.
if (useAfter) place <- newPlace + 1 # Overriding place.
}
# Making the new column.
data[, colName] <- colData
# Finding out how to reorder this.
# The if statement handles the case where place = 1.
currentPlace <- length(names(data)) # Getting the place of our data (which should have been just added at the end).
if (place == 1) {
colOrder <- c(currentPlace, 1:(currentPlace - 1))
} else if (place == currentPlace) { # If the place to add the new data was just at the end of the data. Which is stupid...but we'll add support anyway.
colOrder <- 1:currentPlace
} else { # Every other case.
firstHalf <- 1:(place - 1) # Finding the first half on columns that come before the insertion.
secondHalf <- place:(currentPlace - 1) # Getting the second half, which comes after the insertion.
colOrder <- c(firstHalf, currentPlace, secondHalf) # Putting that order together.
}
# Reordering the data.
data <- subset(data, select = colOrder)
# Data Table compatability.
if (dClass[1] == "data.table") data <- as.data.table(data)
# Returning.
return(data)
}
我发现我还没有包括CheckChoice:
#####
# FUNCTION: CheckChoice(names, dataNames, firstWord == "Oops" message = TRUE)
# DESCRIPTION: Takes the column names of a data frame and checks to make sure whatever "choice" you made (be it
# your choice of dummies or your choice of chops) is actually in the data frame columns. Makes troubleshooting easier.
# This function is also important in prechecking names to make sure the formula ends up being right. Use it after
# adding in new data to check the "choose" options. Set firstWord to the first word you want said before an exclamation point.
# The warn argument (previously message) can be set to TRUE if you only want to
#####
CheckChoice <- function(names, dataNames, firstWord = "Oops", warn = FALSE) {
for (name in names) {
if (warn == TRUE) { if(!(name %in% dataNames)) { warning(paste0(firstWord, "! The column/value/argument, ", name, ", was not valid OR not in your data! Check your input! This is a warning message of that!")) } }
if (warn == FALSE) { if(!(name %in% dataNames)) { stop(paste0(firstWord, "! The column/value/argument, " , name, ", was not valid OR not in your data! Check your input!")) } }
}
}
- giraffehere
2
我会简单地使用cbind()函数实现这个操作：
> df <- data.frame(a=1:5,
+ b=10:14,
+ c=rep(0,5),
+ d=7:11)
>
> z <- LETTERS[1:5]
> df <- cbind(df[,1:2], z, df[,3:4]) # Puts the z column between 2nd and 3rd column of df
> df
a b z c d
1 1 10 A 0 7
2 2 11 B 0 8
3 3 12 C 0 9
4 4 13 D 0 10
5 5 14 E 0 11
- Md Ahsanul Himel
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