R语言因子

发布于 2016-01-02 09:29:37 | 471 次阅读 | 评论: 0 | 来源: 网络整理

因子是它们用于将数据进行分类并将其存储为级别的数据对象。它们可以同时存储字符串和整数。它们在具有唯一值的有限数目的列是有用的。 例如，"male, "Female" 和 True, False 等. 它们在统计建模的数据分析非常有用。

使用 factor() 函数通过采取向量作为输入来创建因子。

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))

 [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

在数据帧的因子

在创建任何数据帧文本数据的列，R语言对待文本列作为分类数据，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)

  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

更改级别的顺序

一个因素中的级别的顺序可以通过使用级别的新顺序，再次应用因子函数来改变。

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)

 [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

生成因子级别

我们可以通过使用 gl()函数生成因子的级别。它有两个整型输入，表示每个级别有多少水平和多少次。

语法

gl(n, k, labels)

以下是所使用的参数的说明：

• n 是一个整数来给出级别数
• k 是一个整数给出重复的数量
• labels 为所得到的因子级别标签的向量。

示例

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

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