R-在字符串中添加前导零，没有固定的字符串格式 [英] R-- Add leading zero to string, with no fixed string format

问题描述

我有一列如下.

9453、55489、4588、18893、4457、2339、45489HQ，7833HQ

9453, 55489, 4588, 18893, 4457, 2339, 45489HQ, 7833HQ

如果数字少于5位，我想添加前导零.但是，有些数字最后带有"HQ"，有些则没有.(我检查了其他帖子，它们在"HQ"部分没有类似的问题)

I would like to add leading zero if the number is less than 5 digits. However, some numbers have "HQ" in the end, some don't.(I did check other posts, they dont have similar problem in the "HQ" part)

所以最终所需的输出应该是:

so the finally desired output should be:

09453、55489、04588、18893、04457、02339、45489HQ，07833HQ

09453, 55489, 04588, 18893, 04457, 02339, 45489HQ, 07833HQ

您知道如何执行此操作吗?非常感谢您阅读我的帖子！

any idea how to do this? Thank you so much for reading my post!

推荐答案

使用正则表达式的单行代码:

A one-liner using regular expressions:

my_strings <- c("9453", "55489", "4588", 
      "18893", "4457", "2339", "45489HQ", "7833HQ")

gsub("^([0-9]{1,4})(HQ|$)", "0\\1\\2",my_strings)

[1] "09453"   "55489"   "04588"   "18893"   
    "04457"   "02339"   "45489HQ" "07833HQ"

说明:

^ start of string
[0-9]{1,4} one to four numbers in a row
(HQ|$) the string "HQ" or the end of the string

括号表示顺序的捕获组.因此，0\\1\\2表示0，后跟第一个捕获组[0-9]{1,4}和第二个捕获组HQ|$.

Parentheses represent capture groups in order. So 0\\1\\2 means 0 followed by the first capture group [0-9]{1,4} and the second capture group HQ|$.

当然，如果有5个数字，则表示正则表达式不匹配，因此不会更改.

Of course if there is 5 numbers, then the regex isn't matched, so it doesn't change.

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