我有一个包含a，b和c列的数据框。我想在b和c之间添加一个新列。
我知道我最后可以使用 cbind 添加d但是如何在两列之间插入呢？
答案 0 :(得分：58)
我建议您使用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，您可以使用列名而不是列索引：
add_column(dataset, d = 4:8, .after = "b")
如果更方便，可以使用参数.before代替.after。
add_column(dataset, d = 4:8, .before = "c")
答案 1 :(得分：29)
添加新专栏：
df$d <- list/data
然后你可以重新排序它们。
df <- df[, c("a", "b", "d", "c")]
答案 2 :(得分：19)
您可以使用[重新排序列，或者按照您想要的顺序显示列。
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
答案 3 :(得分：11)
假设c始终紧跟在b之后，此代码将在b之后添加一列，无论您的data.frame中的b位于何处。
> 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
或者可能更自然：
data.frame(append(test, list(d=2), after=match("b", names(test))))
答案 4 :(得分：4)
创建一个示例data.frame并向其添加一列。
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)]]
或按列名
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
答案 5 :(得分：3)
您想将列z添加到旧数据框（old.df） 由列x和y定义。
z = rbinom(1000, 5, 0.25)
old.df <- data.frame(x = c(1:1000), y = rnorm(1:1000))
head(old.df)
定义一个名为new.df的新数据框
new.df <- data.frame(x = old.df[,1], z, y = old.df[,2])
head(new.df)
答案 6 :(得分：2)
为了它的价值，我写了一个函数来做到这一点：
[移除]
我现在已使用before和after功能更新此功能，并将place默认为1.它还具有数据表兼容性：
#####
# 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)
}
我意识到我也没有包括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!")) } }
}
}
答案 7 :(得分：1)
这是一种在数据框上的特定位置插入列的快速而肮脏的方法。在我的情况下，我在原始数据框中有5列：c2b我将在c2和c3之间插入新列> 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
。
1）让我们首先创建测试数据框：
c2b 2）在我们的数据框末尾添加新列> 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
：
c(1:2, 6, 3:5) 3）根据列索引重新排序数据框。在我的例子中，我想在现有的第2列和第3列之间插入新列（6）。我通过使用相当于c(1, 2, 6, 3, 4, 5)的向量> 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
来寻址数据框中的列来实现这一点。
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<p>this is paragraph one</p>
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有！
答案 8 :(得分：1)
此函数在数据框中所有预先存在的列之间插入一个零列。
insertaCols<-function(dad){
nueva<-as.data.frame(matrix(rep(0,nrow(daf)*ncol(daf)*2 ),ncol=ncol(daf)*2))
for(k in 1:ncol(daf)){
nueva[,(k*2)-1]=daf[,k]
colnames(nueva)[(k*2)-1]=colnames(daf)[k]
}
return(nueva)
}
答案 9 :(得分：1)
以下是如何将列从最后一个位置移动到第一个位置的示例。它将[与ncol结合在一起。我认为在这里为忙碌的读者提供一个非常简短的答案是有用的：
d = mtcars
d[, c(ncol(d), 1:(ncol(d)-1))]
答案 10 :(得分：1)
您可以使用append()函数将项目插入向量或列表（数据帧为列表）。简单地：
df <- data.frame(a=c(1,2), b=c(3,4), c=c(5,6))
df <- as.data.frame(append(df, list(d=df$b+df$c), after=2))
或者，如果要通过名称指定位置，请使用which：
df <- as.data.frame(append(df, list(d=df$b+df$c), after=which(names(df)=="b")))
答案 11 :(得分：0)
如果您不能假设列b在c之前，可以使用match查找两者的列号，min获取较低的列号， seq_len获取序列，直到此列为止。然后，您可以先将该索引用作阳性子集，然后放置新列d，然后再将该序列用作 negative 子集。
i <- seq_len(min(match(c("b", "c"), colnames(x))))
data.frame(x[i], d, x[-i])
#cbind(x[i], d, x[-i]) #Alternative
# a b d c
#1 1 4 10 7
#2 2 5 11 8
#3 3 6 12 9
如果您知道列b在c之前，可以将新列d放在b之后：
i <- seq_len(match("b", colnames(x)))
data.frame(x[i], d, x[-i])
# a b d c
#1 1 4 10 7
#2 2 5 11 8
#3 3 6 12 9
数据：
x <- data.frame(a = 1:3, b = 4:6, c = 7:9)
d <- 10:12
答案 12 :(得分：0)
df <- data.frame(a=c(1,2), b=c(3,4), c=c(5,6))
df %>%
mutate(d= a/2) %>%
select(a, b, d, c)
结果
a b d c
1 1 3 0.5 5
2 2 4 1.0 6
我建议在dplyr::select之后使用dplyr::mutate。它有很多帮助者可以选择/取消选择列的子集。
在此问题的上下文中，您选择的顺序将反映在输出data.frame中。
答案 13 :(得分：0)
简单的解决方案。在具有5列的数据框中，如果要在3到4之间插入另一列...
tmp <- data[, 1:3]
tmp$example <- NA # or any value.
data <- cbind(tmp, data[, 4:5]
答案 14 :(得分：0)
你可以像下面这样做 -
df <- data.frame(a=1:4, b=5:8, c=9:12)
df['d'] <- seq(10,13)
df <- df[,c('a','b','d','c')]
答案 15 :(得分：0)
R没有指定添加新列的位置的功能。例如，mtcars$mycol<-'foo'。它总是作为最后一列添加。使用其他方法（例如dplyr's select()），您可以将mycol移动到所需位置。这并不理想，R可能希望将来尝试改变它。
答案 16 :(得分：0)
`
data1 <- data.frame(col1=1:4, col2=5:8, col3=9:12)
row.names(data1) <- c("row1","row2","row3","row4")
data1
data2 <- data.frame(col1=21:24, col2=25:28, col3=29:32)
row.names(data2) <- c("row1","row2","row3","row4")
data2
insertPosition = 2
leftBlock <- unlist(data1[,1:(insertPosition-1)])
insertBlock <- unlist(data2[,1:length(data2[1,])])
rightBlock <- unlist(data1[,insertPosition:length(data1[1,])])
newData <- matrix(c(leftBlock, insertBlock, rightBlock), nrow=length(data1[,1]), byrow=FALSE)
newData
`