R - 因素

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因素是用于对数据进行分类并将其存储为级别的数据对象。它们可以存储字符串和整数。它们在具有有限数量的唯一值的列中非常有用。像“男性”、“女性”和“真”、“假”等。它们在统计建模的数据分析中很有用。

因子是使用Factor ()函数通过将向量作为输入来创建的。

例子

# Create a vector as input.
data <- c("East","West","East","North","North","East","West","West","West","East","North")

print(data)
print(is.factor(data))

# Apply the factor function.
factor_data <- factor(data)

print(factor_data)
print(is.factor(factor_data))

当我们执行上面的代码时，它会产生以下结果 -

[1] "East"  "West"  "East"  "North" "North" "East"  "West"  "West"  "West"  "East" "North"
[1] FALSE
[1] East  West  East  North North East  West  West  West  East  North
Levels: East North West
[1] TRUE

数据框中的因素

在创建任何包含文本数据列的数据框时，R 会将文本列视为分类数据并在其上创建因子。

# Create the vectors for data frame.
height <- c(132,151,162,139,166,147,122)
weight <- c(48,49,66,53,67,52,40)
gender <- c("male","male","female","female","male","female","male")

# Create the data frame.
input_data <- data.frame(height,weight,gender)
print(input_data)

# Test if the gender column is a factor.
print(is.factor(input_data$gender))

# Print the gender column so see the levels.
print(input_data$gender)

当我们执行上面的代码时，它会产生以下结果 -

  height weight gender
1    132     48   male
2    151     49   male
3    162     66 female
4    139     53 female
5    166     67   male
6    147     52 female
7    122     40   male
[1] TRUE
[1] male   male   female female male   female male  
Levels: female male

更改级别顺序

可以通过使用新的级别顺序再次应用因子函数来更改因子中级别的顺序。

data <- c("East","West","East","North","North","East","West",
   "West","West","East","North")
# Create the factors
factor_data <- factor(data)
print(factor_data)

# Apply the factor function with required order of the level.
new_order_data <- factor(factor_data,levels = c("East","West","North"))
print(new_order_data)

当我们执行上面的代码时，它会产生以下结果 -

 [1] East  West  East  North North East  West  West  West  East  North
Levels: East North West
 [1] East  West  East  North North East  West  West  West  East  North
Levels: East West North

生成因子水平

我们可以使用gl()函数生成因子水平。它需要两个整数作为输入，表示有多少级别以及每个级别的次数。

句法

gl(n, k, labels)

以下是所使用参数的描述 -

• n是给出级别数的整数。

• k是给出重复次数的整数。

• labels是结果因子水平的标签向量。

例子

v <- gl(3, 4, labels = c("Tampa", "Seattle","Boston"))
print(v)

当我们执行上面的代码时，它会产生以下结果 -

Tampa   Tampa   Tampa   Tampa   Seattle Seattle Seattle Seattle Boston 
[10] Boston  Boston  Boston 
Levels: Tampa Seattle Boston