# R语言 因子

2021-12-27 09:29 更新

## 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
```

## 数据帧的因子

``````# 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)
```

``` [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

### 语法

```gl(n, k, labels)
```

• n是给出级数的整数。

• k是给出复制数目的整数。

• labels是所得因子水平的标签向量。

### 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
```

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