在字符串中添加前导零

我有一系列我想要标准化的列名.

names <- c("apple", "banana", "orange", "apple1", "apple2", "apple10", "apple11", "banana2", "banana12")

我希望任何具有一位数字的东西都用零填充,所以

apple
banana
orange
apple01
apple02
apple10
apple11
banana02
...

我一直在努力使用 stringr

strdouble <- str_detect(names, "[0-9]{2}")
strsingle <- str_detect(names, "[0-9]")

str_detect(names[strsingle & !strdouble])

但无法弄清楚如何有选择地替换/预先...

你可以使用sub("([a-z])([0-9])$","\\10\\2",names):

[1] "apple"    "banana"   "orange"   "apple01"  "apple02"  "apple10"  "apple11"  "banana02"
[9] "banana12"

它只更改字母后面有一个数字的名称($字符串的结尾).

该\\1选择在第一块():字母.然后它将前导0,然后是第二个块放入():数字.

这是一个使用负前瞻和后置断言来识别单个数字的选项.

gsub('(?