R Language Learning (7) strings and factors

Strings and factors

1. String

Create a string

> C ("Hello", "World")
[1] "Hello" "World"

Paste () function connection string

> C ("Hello", "World")
[1] "Hello" "World"
> Paste (C ("Hello", "Hi"), "World")
[1] "Hello World", "Hi World"
> Paste (C ("Hello", "Hi"), "World", sep= "-")
[1] "Hello-world" "Hi-world"

> Paste (C ("Hello", "Hi"), "world", collapse = ",")
[1] "Hello World,hi World"
> Paste0 (C ("Hello", "Hi"), "World") #paste0函数能去掉分隔符
[1] "HelloWorld" "Hiworld"

The ToString () function prints a string

> x
[1] 1 4 9 16 25
> toString (x)
[1] "1, 4, 9, 16, 25"
> toString (x,width = 4)
[1] "1,...."
> toString (x,width = ten) #width表示限制字符长度
[1] "1, 4, ...."

2. Formatting numbers

FORMATC function

> Pow <-1:3
> (powers_of_e <-exp (POW))
[1] 2.718282 7.389056 20.085537
> FORMATC (powers_of_e)
[1] "2.718" "7.389" "20.09"
> formatc (powers_of_e,digits = 3) #指定3个数字

[1] "2.72" "7.39" "20.1"
> formatc (powers_of_e,digits = 3,width = ten) #前面加上一个空格
[1] "2.72" "7.39" "20.1"
> formatc (powers_of_e,digits = 3,format = "E") #科学格式
[1] "2.718e+00" "7.389e+00" "2.009e+01"
> formatc (powers_of_e,digits = 3,flag = "+") #前面加上 +
[1] "+2.72" "+7.39" "+20.1"

sprintf function

> sprintf ("%s%d =%f", "Euler's constant to the power", pow,powers_of_e)
[1] "Euler's constant to the power 1 = 2.718282"
[2] "Euler's constant to the power 2 = 7.389056"
[3] "Euler's constant to the power 3 = 20.085537"

There are also format (similar to FORMATC usages) and prettynum (formatted very large or very small numbers) where two functions can format numbers.

Change case

> ToUpper ("I am the King of the World")
[1] "I AM the KING of the World"
> ToLower ("HELLO World")
[1] "Hello World"

3. Factor factor: A special variable type used to store class variables.

Create factor data frame internal auto create factor

> (Heights <-data.frame (height_cm = C (153,181,150,172,165,149,174,169,198,163), gender = C ("female", "male", " Female "," male "," male "," female "," female "," male "," male "," female ")))
HEIGHT_CM gender
1 153 Female
2 181 Male
3 Female
4 172 Male
5 165 Male
6 149 Female
7 174 Female
8 169 Male
9 198 Male
Ten 163 female
> class (Heights$gender)
[1] "factor"#是一个因子
> Heights$gender
[1] Female male female male male female female male male
[Ten] Female
Levels:female Male
> Levels (Heights$gender)#female和male被称为因子水平
[1] "female" "male"

Factor function Creation factor

> GENDER_FAC <-C ("female", "male", "female", "male", "male")
> (Gender_char <-Factor (GENDER_FAC))
[1] Female male female male male
Levels:female Male

R Language Learning (7) strings and factors