我有一个包含 a、b 和 c 列的数据框。我想在 b 和 c 之间添加一个新的 d 列。
我知道我可以使用cbind在最后添加 d但如何将它插入两列之间？
问问题
153088 次
18 回答
97
我建议您使用包中的add_column()功能tibble。
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")
或者使用参数.before而不是.after如果更方便。
add_column(dataset, d = 4:8, .before = "c")
于 2016-11-24T14:46:28.750 回答
51
在您的新列中添加：
df$d <- list/data
然后你可以重新排序它们。
df <- df[, c("a", "b", "d", "c")]
于 2013-07-11T02:14:16.940 回答
26
您可以使用 [ 重新排序列，或按您想要的顺序显示列。
d <- data.frame(a=1:4, b=5:8, c=9:12)
target <- which(names(d) == 'b')[1]
cbind(d[,1:target,drop=F], data.frame(d=12:15), d[,(target+1):length(d),drop=F])
a b d c
1 1 5 12 9
2 2 6 13 10
3 3 7 14 11
4 4 8 15 12
于 2012-11-21T22:03:48.610 回答
17
假设c总是紧随其后，无论您的data.frame中的哪个位置b，此代码都会在之后添加一列。bb
> test <- data.frame(a=1,b=1,c=1)
> test
a b c
1 1 1 1
> bspot <- which(names(test)=="b")
> data.frame(test[1:bspot],d=2,test[(bspot+1):ncol(test)])
a b d c
1 1 1 2 1
或者可能更自然：
data.frame(append(test, list(d=2), after=match("b", names(test))))
于 2012-11-21T22:08:33.787 回答
9
创建一个示例 data.frame 并向其中添加一列。
df = data.frame(a = seq(1, 3), b = seq(4,6), c = seq(7,9))
df['d'] <- seq(10,12)
df
a b c d
1 1 4 7 10
2 2 5 8 11
3 3 6 9 12
按列索引重新排列
df[, colnames(df)[c(1:2,4,3)]]
或按列名
df[, c('a', 'b', 'd', 'c')]
结果是
a b d c
1 1 4 10 7
2 2 5 11 8
3 3 6 12 9
于 2016-08-15T14:16:08.533 回答
4
您想将 z 列添加到由 x 和 y 列定义的旧数据框 (old.df)。
z = rbinom(1000, 5, 0.25)
old.df <- data.frame(x = c(1:1000), y = rnorm(1:1000))
head(old.df)
定义一个名为 new.df 的新数据框
new.df <- data.frame(x = old.df[,1], z, y = old.df[,2])
head(new.df)
于 2013-07-11T02:57:08.897 回答
4
这是在数据框的特定位置插入列的一种快速而肮脏的方法。就我而言，我在原始数据框中有 5 列：我将在和之间c1, c2, c3, c4, c5插入一个新列。c2bc2c3
1）让我们首先创建测试数据框：
> dataset <- data.frame(c1 = 1:5, c2 = 2:6, c3=3:7, c4=4:8, c5=5:9)
> dataset
c1 c2 c3 c4 c5
1 1 2 3 4 5
2 2 3 4 5 6
3 3 4 5 6 7
4 4 5 6 7 8
5 5 6 7 8 9
c2b2）在我们的数据框末尾添加新列：
> dataset$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
3）根据列索引对数据框重新排序。就我而言，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c(1:2, 6, 3:5)相当于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
那里！
于 2016-03-11T18:20:48.637 回答
3
轻松解决。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]
于 2018-07-10T11:47:06.207 回答
2
为了它的价值，我写了一个函数来做到这一点：
[已删除]
我现在已经用before和功能更新了这个函数after，默认place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!")) } }
}
}
于 2016-01-11T18:41:19.830 回答
2
我会简单地使用cbind()这个：
> 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
于 2021-09-29T05:42:15.080 回答
1
这是一个如何将列从最后一个位置移动到第一个位置的示例。它[与ncol. 我认为在这里为忙碌的读者提供一个非常简短的答案会很有用：
d = mtcars
d[, c(ncol(d), 1:(ncol(d)-1))]
于 2018-03-30T18:14:42.483 回答
1
您可以使用该append()函数将项目插入向量或列表（数据框是列表）。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$c), after=2))
或者，如果您想按名称指定位置，请使用which：
df <- as.data.frame(append(df, list(d=df$b+df$c), after=which(names(df)=="b")))
于 2019-03-27T07:54:21.740 回答
1
此函数在数据框中的所有预先存在的列之间插入一个零列。
insertaCols<-function(dad){
nueva<-as.data.frame(matrix(rep(0,nrow(daf)*ncol(daf)*2 ),ncol=ncol(daf)*2))
for(k in 1:ncol(daf)){
nueva[,(k*2)-1]=daf[,k]
colnames(nueva)[(k*2)-1]=colnames(daf)[k]
}
return(nueva)
}
于 2016-04-24T05:02:41.960 回答
0
`
data1 <- data.frame(col1=1:4, col2=5:8, col3=9:12)
row.names(data1) <- c("row1","row2","row3","row4")
data1
data2 <- data.frame(col1=21:24, col2=25:28, col3=29:32)
row.names(data2) <- c("row1","row2","row3","row4")
data2
insertPosition = 2
leftBlock <- unlist(data1[,1:(insertPosition-1)])
insertBlock <- unlist(data2[,1:length(data2[1,])])
rightBlock <- unlist(data1[,insertPosition:length(data1[1,])])
newData <- matrix(c(leftBlock, insertBlock, rightBlock), nrow=length(data1[,1]), byrow=FALSE)
newData
`
于 2015-05-22T08:07:56.207 回答
0
df <- data.frame(a=c(1,2), b=c(3,4), c=c(5,6))
df %>%
mutate(d= a/2) %>%
select(a, b, d, c)
结果
a b d c
1 1 3 0.5 5
2 2 4 1.0 6
我建议dplyr::select在dplyr::mutate. 它有许多帮助器来选择/取消选择列的子集。
在这个问题的上下文中，您选择的顺序将反映在输出 data.frame 中。
于 2019-07-30T05:41:34.680 回答
0
R 没有指定添加新列的位置的功能。例如，mtcars$mycol<-'foo'。它总是作为最后一列添加。使用其他方式（例如dplyr's select()），您可以将 mycol 移动到所需位置。这并不理想，R 可能希望在未来尝试改变它。
于 2016-07-15T17:14:06.063 回答
0
当你不能假设列b出现之前，c你可以使用match查找两者的列号，min获取较低的列号并seq_len获取直到该列的序列。然后您可以先将此索引用作正子集，然后放置新列d，然后再次将序列用作负子集。
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
如果您知道该列出现在您可以将新列放在b之后：cdb
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
于 2020-07-06T07:52:32.570 回答
0
你可以像下面那样做 -
df <- data.frame(a=1:4, b=5:8, c=9:12)
df['d'] <- seq(10,13)
df <- df[,c('a','b','d','c')]
于 2018-04-26T16:10:32.567 回答