在R中添加前导0

乔伊·加萨雷利（Joey Garzarelli）

我有一个很大的数据框，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，问题仅在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

我已经研究了sprintf和FormatC功能，但仍然没有运气。

彼得·L

带有嵌套gsub调用的强制方法：

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"

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