因子是它們用於將數據進行分類並將其存儲為級彆的數據對象。它們可以同時存儲字符串和整數。它們在具有唯一值的有限數目的列是有用的。 例如，"male, "Female" 和 True, False 等. 它們在統計建模的數據分析非常有用。

使用 factor() 函數通過采取向量作為輸入來創建因子。

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))

當我們上麵的代碼執行時，它產生以下結果：

 [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

在數據幀的因子

在創建任何數據幀文本數據的列，R語言對待文本列作為分類數據，並在其上創建因子。

# 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)

當我們上麵的代碼執行時，它產生以下結果：

  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

更改級彆的順序

一個因素中的級彆的順序可以通過使用級彆的新順序，再次應用因子函數來改變。

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)

當我們上麵的代碼執行時，它產生以下結果：

 [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

生成因子級彆

我們可以通過使用 gl()函數生成因子的級彆。它有兩個整型輸入，表示每個級彆有多少水平和多少次。

語法

gl(n, k, labels)

以下是所使用的參數的說明：

• n 是一個整數來給出級彆數
• k 是一個整數給出重複的數量
• labels 為所得到的因子級彆標簽的向量。

示例

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

當我們上麵的代碼執行時，它產生以下結果：

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