r - 在 r 中添加前导 0

Question

我有一个大型数据框，其中填充了以下字符:

 x <- c("Y188","Y204" ,"Y221","EP121_1" ,"Y233" , "Y248" ,"Y268", "BB2","BB20",  
 "BB32" ,"BB044" ,"BB056" , "Y234" , "Y249" ,"Y271" ,"BB3", "BB21", "BB33",
 "BB045","BB057" ,"Y236", "Y250", "Y272" , "BB4", "BB22" )

如您所见，某些标签(例如 BB20)只有两个整数。我希望整个字符列表至少有 3 个这样的整数(如果有帮助，问题只出现在 BB 标签中):

Y188, Y204, Y221, EP121_1, Y233, Y248, Y268, BB002, BB020, BB032, BB044,
BB056, Y234, Y249, Y271, BB003, BB021, BB033, BB045, BB057, Y236, Y250,
Y272, BB004, BB022 

我研究了 sprintf 和 FormatC 函数，但仍然没有成功。

Answer 1

使用嵌套 gsub 调用的有效方法:

gsub("(.*[A-Z])(\\d{1}$)", "\\100\\2",
     gsub("(.*[A-Z])(\\d{2}$)", "\\10\\2", x))
# [1] "Y188"    "Y204"    "Y221"    "EP121_1" "Y233"    "Y248"    "Y268"    "BB002"   "BB020"  
# [10] "BB032"   "BB044"   "BB056"   "Y234"    "Y249"    "Y271"    "BB003"   "BB021"   "BB033"  
# [19] "BB045"   "BB057"   "Y236"    "Y250"    "Y272"    "BB004"   "BB022"