R語言因子

因子是用於對資料進行分類並將其儲存為級別的資料物件。它們可以儲存字串和整數。 它們在具有有限數量的唯一值的列中很有用。 像「男」，「女」，「真」，「假」等。它們在統計建模的資料分析中很有用。

因子可通過factor()函式使用向量作為輸入來建立。

範例

# 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))

當我們執行上述程式碼時，會產生以下結果 -

 [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

在資料影格中的因子

在使用一列文字資料建立資料影格時，R將文字列視為分類資料並在其上建立因子。參考以下範例程式碼 -

# 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)

當我們執行上述程式碼時，會產生以下結果 -

  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

改變級別順序

可以通過用新的級別順序再次應用因子函式來改變因子中級別的順序。參考以下實現程式碼 -

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)

當我們執行上述程式碼時，會產生以下結果 -

 [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

產生因子級別

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

語法

gl(n, k, labels)

以下是使用的引數的描述 -

• n - 是給出級別數的整數。
• k - 是給出複製次數的整數。
• labels - 是所得因子水平的標籤向量。

例子

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

當我們執行上述程式碼時，會產生以下結果 -

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