因子是用于對數(shù)據(jù)進(jìn)行分類并將其存儲為級別的數(shù)據(jù)對象。它們可以存儲字符串和整數(shù)。 它們在具有有限數(shù)量的唯一值的列中很有用。 像“男”，“女”，“真”，“假”等。它們在統(tǒng)計建模的數(shù)據(jù)分析中很有用。

因子可通過factor()函數(shù)使用向量作為輸入來創(chuàng)建。

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(dāng)我們執(zhí)行上述代碼時，會產(chǎn)生以下結(jié)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(shù)據(jù)幀中的因子

在使用一列文本數(shù)據(jù)創(chuàng)建數(shù)據(jù)幀時，R將文本列視為分類數(shù)據(jù)并在其上創(chuàng)建因子。參考以下示例代碼 -

# 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(dāng)我們執(zhí)行上述代碼時，會產(chǎn)生以下結(jié)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

改變級別順序

可以通過用新的級別順序再次應(yīng)用因子函數(shù)來改變因子中級別的順序。參考以下實(shí)現(xiàn)代碼 -

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(dāng)我們執(zhí)行上述代碼時，會產(chǎn)生以下結(jié)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

產(chǎn)生因子級別

可以通過使用gl()函數(shù)來生成因子級別。它需要兩個整數(shù)作為輸入，它表示每個級別有多少級別和多少次。

語法

gl(n, k, labels)

以下是使用的參數(shù)的描述 -

• n - 是給出級別數(shù)的整數(shù)。
• k - 是給出復(fù)制次數(shù)的整數(shù)。
• labels - 是所得因子水平的標(biāo)簽向量。

例子

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

當(dāng)我們執(zhí)行上述代碼時，會產(chǎn)生以下結(jié)果 -

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