1. WIKI教程
2. 学习R编程
3. R - Factors

R - Factors

因素是数据对象，用于对数据进行分类并将其存储为级别。 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很有用。 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。

通过将矢量作为输入，使用factor ()函数创建factor () 。

例子 (Example)

# 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

数据框架中的因素

在使用一列文本数据创建任何数据框时，R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

改变级别顺序

通过使用新的级别顺序再次应用因子函数，可以改变因子中级别的顺序。

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()函数生成因子级别。 它需要两个整数作为输入，表示每个级别有多少级别和多少次。

语法 (Syntax)

gl(n, k, labels)

以下是所用参数的说明 -

• n是一个给出级别数的整数。

• k是给出复制次数的整数。

• labels是结果因子水平的标签矢量。

例子 (Example)

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