字符串和因子
1.字符串
创建字符串
> c("HELLO","WORLD")
[1] "HELLO" "WORLD"
使用paste函数连接字符串
> 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"
toString函数打印字符串
> x
[1] 1 4 9 16 25
> toString(x)
[1] "1, 4, 9, 16, 25"
> toString(x,width=2) #width表示限制字符长度
[1] "1,...."
toupper、tolower函数更改大小写
> toupper("hello world!")
[1] "HELLO WORLD!"
> tolower("HELLO WORLD!")
[1] "hello world!"
使用substring、substr截取字符串
使用strsplit分割字符串
2.格式化数字
formatC函数
> pow <- 1:3
> (power_of_e <- exp(pow))
[1] 2.718282 7.389056 20.085537
> formatC(power_of_e)
[1] "2.718" "7.389" "20.09"
> formatC(power_of_e,digits=3) #保留三个数字
[1] "2.72" "7.39" "20.1"
> formatC(power_of_e,digits=3,width=10) #在前面添加空格
[1] " 2.72" " 7.39" " 20.1"
> formatC(power_of_e,digits=3,format="e") #科学计数法
[1] "2.718e+00" "7.389e+00" "2.009e+01"
> formatC(power_of_e,digits=3,flag="+") +前面加上+
[1] "+2.72" "+7.39" "+20.1"
sprintf函数
> sprintf("%s %d %e", "Euler‘s constant to the power",pow,power_of_e)
[1] "Euler‘s constant to the power 1 2.718282e+00"
[2] "Euler‘s constant to the power 2 7.389056e+00"
[3] "Euler‘s constant to the power 3 2.008554e+01"
还有format和prettyNum函数用于格式化数字
3.因子：因子是一个用于存储类别变量的特殊的变量类型，有时像字符串，有时像整数
创建因子
数据框自动创建因子
> (heights <- data.frame(height_cm = c(153,181,150,172,165),gender = c("female","male","male","female","male")))height_cm gender
1 153 female
2 181 male
3 150 male
4 172 female
5 165 male
> class(heights$gender)
[1] "factor"
> heights$gender
[1] female male male female male
Levels: female male #female和male称为因子水平
factor函数创建因子
> gender_char <- c("female","male","male","female","male")> (gender_factor <- factor(gender_char))
[1] female male male female male
Levels: female male
R语言学习(5)-字符串和因子,布布扣,bubuko.com