Question

我有一个R数据框，其中包含我想要“展开”的因子，因此对于每个因子级别，新数据框中都有一个关联列，其中包含1/0指示符。例如，假设我有：

df.original <-data.frame(eggs = c("foo", "foo", "bar", "bar"), ham = c(1,2,3,4))

我想：

df.desired  <- data.frame(foo = c(1,1,0,0), bar=c(0,0,1,1), ham=c(1,2,3,4))

因为对于某些需要完全数字数据框的分析（例如，主成分分析），我认为这个特性可能是内置的。写一个函数来做这个不应该太难，但我可以预见到与列名相关的一些挑战，如果已存在某些问题，我宁愿使用它。

Answer 1

使用model.matrix功能：

model.matrix( ~ Species - 1, data=iris )

Answer 2

如果您的数据框仅由因子组成（或者您正在处理所有因素的变量子集），您还可以使用acm.disjonctif包中的ade4函数：

R> library(ade4)
R> df <-data.frame(eggs = c("foo", "foo", "bar", "bar"), ham = c("red","blue","green","red"))
R> acm.disjonctif(df)
  eggs.bar eggs.foo ham.blue ham.green ham.red
1        0        1        0         0       1
2        0        1        1         0       0
3        1        0        0         1       0
4        1        0        0         0       1

不完全是你描述的情况，但它也很有用......

Answer 3

使用reshape2包的快捷方式：

require(reshape2)

> dcast(df.original, ham ~ eggs, length)

Using ham as value column: use value_var to override.
  ham bar foo
1   1   0   1
2   2   0   1
3   3   1   0
4   4   1   0

请注意，这会精确生成所需的列名称。

Answer 4

可能虚拟变量与您想要的类似。然后，model.matrix非常有用：

> with(df.original, data.frame(model.matrix(~eggs+0), ham))
  eggsbar eggsfoo ham
1       0       1   1
2       0       1   2
3       1       0   3
4       1       0   4

Answer 5

来自class.ind包

的晚期作品nnet

library(nnet)
 with(df.original, data.frame(class.ind(eggs), ham))
  bar foo ham
1   0   1   1
2   0   1   2
3   1   0   3
4   1   0   4

Answer 6

刚刚遇到这个旧线程并认为我添加了一个利用ade4来获取由因子和/或数字数据组成的数据帧的函数，并返回一个带有因子作为伪代码的数据帧。

dummy <- function(df) {  

    NUM <- function(dataframe)dataframe[,sapply(dataframe,is.numeric)]
    FAC <- function(dataframe)dataframe[,sapply(dataframe,is.factor)]

    require(ade4)
    if (is.null(ncol(NUM(df)))) {
        DF <- data.frame(NUM(df), acm.disjonctif(FAC(df)))
        names(DF)[1] <- colnames(df)[which(sapply(df, is.numeric))]
    } else {
        DF <- data.frame(NUM(df), acm.disjonctif(FAC(df)))
    }
    return(DF)
}

我们试一试。

df <-data.frame(eggs = c("foo", "foo", "bar", "bar"), 
            ham = c("red","blue","green","red"), x=rnorm(4))     
dummy(df)

df2 <-data.frame(eggs = c("foo", "foo", "bar", "bar"), 
            ham = c("red","blue","green","red"))  
dummy(df2)

Answer 7

这是一种更清晰的方法。我使用model.matrix创建虚拟布尔变量，然后将其合并回原始数据帧。

df.original <-data.frame(eggs = c("foo", "foo", "bar", "bar"), ham = c(1,2,3,4))
df.original
#   eggs ham
# 1  foo   1
# 2  foo   2
# 3  bar   3
# 4  bar   4

# Create the dummy boolean variables using the model.matrix() function.
> mm <- model.matrix(~eggs-1, df.original)
> mm
#   eggsbar eggsfoo
# 1       0       1
# 2       0       1
# 3       1       0
# 4       1       0
# attr(,"assign")
# [1] 1 1
# attr(,"contrasts")
# attr(,"contrasts")$eggs
# [1] "contr.treatment"

# Remove the "eggs" prefix from the column names as the OP desired.
colnames(mm) <- gsub("eggs","",colnames(mm))
mm
#   bar foo
# 1   0   1
# 2   0   1
# 3   1   0
# 4   1   0
# attr(,"assign")
# [1] 1 1
# attr(,"contrasts")
# attr(,"contrasts")$eggs
# [1] "contr.treatment"

# Combine the matrix back with the original dataframe.
result <- cbind(df.original, mm)
result
#   eggs ham bar foo
# 1  foo   1   0   1
# 2  foo   2   0   1
# 3  bar   3   1   0
# 4  bar   4   1   0

# At this point, you can select out the columns that you want.

Answer 8

我需要一个功能来“爆炸”更灵活的因素，并根据ade4包中的acm.disjonctif函数制作一个。这允许您选择分解值，在acm.disjonctif中为0和1。它只会爆炸具有“少量”水平的因素。保留数字列。

# Function to explode factors that are considered to be categorical,
# i.e., they do not have too many levels.
# - data: The data.frame in which categorical variables will be exploded.
# - values: The exploded values for the value being unequal and equal to a level.
# - max_factor_level_fraction: Maximum number of levels as a fraction of column length. Set to 1 to explode all factors.
# Inspired by the acm.disjonctif function in the ade4 package.
explode_factors <- function(data, values = c(-0.8, 0.8), max_factor_level_fraction = 0.2) {
  exploders <- colnames(data)[sapply(data, function(col){
      is.factor(col) && nlevels(col) <= max_factor_level_fraction * length(col)
    })]
  if (length(exploders) > 0) {
    exploded <- lapply(exploders, function(exp){
        col <- data[, exp]
        n <- length(col)
        dummies <- matrix(values[1], n, length(levels(col)))
        dummies[(1:n) + n * (unclass(col) - 1)] <- values[2]
        colnames(dummies) <- paste(exp, levels(col), sep = '_')
        dummies
      })
    # Only keep numeric data.
    data <- data[sapply(data, is.numeric)]
    # Add exploded values.
    data <- cbind(data, exploded)
  }
  return(data)
}

自动将R因子扩展为每个因子级别的1/0指标变量的集合

8 个答案: