Question

我想编写一个for循环，我需要先将data.frame的某些列的类转换为字符。在一些操作（与此问题无关）之后，我需要将列转换回原始类。

列的转换必须在for循环中完成。我怎么能这样做？

以下是一些数据和示例for循环：

# Example data
data <- data.frame(x1 = as.numeric(1:5), x2 = as.factor(7:3))

for(i in 1:ncol(data)) {

  # Save original class.
  class_col_i <- class(data[ , i])

  # Convert column as character.
  data[ , i] <- as.character(data[ , i])

  # (Here I will do some operations, which are irrelevant for this problem.)

  # Here I need to convert the column back to its original class.
  # How can I do that?

  # data[ , i] <- class_col_i... ???
}

class(data$x1) # This should be a numeric
class(data$x2) # This should be a factor

Answer 1

使用match.fun，请参阅此示例：

#dummy data
d <- mtcars
class(d$gear)
# [1] "numeric"

#change to character
classOrg <- class(d$gear)
d$gear <- as.character(d$gear)
class(d$gear)
# [1] "character"

#do some fun stuff
# ... d$gear 

#convert it back
myConvertFun <- match.fun(paste0("as.", classOrg))
d$gear <- myConvertFun(d$gear)
class(d$gear)
# [1] "numeric"

Answer 2

试试这个：

data <- data.frame(x1 = as.numeric(1:5), x2 = as.factor(7:3))
class_col<-NULL
for(i in 1:ncol(data)) {

# Save original class.
class_col[i] <- class(data[ , i])

# Convert column as character.
data[ , i] <- as.character(data[ , i])

# (Here I will do some operations, which are irrelevant for this    
#problem.)

# Here I need to convert the column back to its original class.
# How can I do that?

class(data[ , i]) <- class_col[i]
}

class(data$x1) # This should be a numeric
class(data$x2)

在for循环中分配不同的类

2 个答案: