R语言 因子

R语言 因子

因子是用于对数据进行分类和存储为级别的数据对象。它们可以存储字符串和整数。它们适用于具有有限数量独特值的列。例如，”男性”，”女性”和True，False等。它们在统计建模的数据分析中非常有用。

因子是通过使用 factor() 函数，以向量作为输入来创建的。

示例

# 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))

执行上面的代码时，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

数据框中的因子

创建带有文本数据列的数据框时，R将该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_datagender))

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

当我们执行上面的代码时，它产生以下结果 −

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

改变水平的顺序

通过再次应用
“`factor“`函数，并使用新的水平顺序，可以改变因子中水平的顺序。

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)

当我们执行上述代码时，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

可以使用 gl() 函数来生成因子水平。它接受两个整数作为输入，表示有多少个水平和每个水平需要重复的次数。

语法

gl(n, k, labels)

以下是参数的描述：

• n 是一个整数，表示级别的数量。

• k 是一个整数，表示重复次数。

• labels 是一个包含结果因子级别标签的向量。

示例

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