在 r 中添加前导 0

Question

我有一个大数据框，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，但仍然没有运气。

Answer 1

带有嵌套 gsub 调用的有力方法：

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"

Answer 2

肯定有更通用的方法来执行此操作，但对于这样的本地化任务，两个简单的 sub 就足够了：为两位数字添加一个尾随零，为一位数字添加两个尾随零数字。

x <- sub("^BB(\d{1})$","BB00\1",x)
x <- sub("^BB(\d{2})$","BB0\1",x)

Answer 3

这可行，但会有边缘情况

# indicator for numeric of length less than three
num <- gsub("[^0-9]", "", x)
id <- nchar(num) < 3

# overwrite relevant values with the reformatted ones
x[id] <- paste0(gsub("[0-9]", "", x)[id],
                     formatC(as.numeric(num[id]), width = 3, flag = "0"))

 [1] "Y188"    "Y204"    "Y221"    "EP121_1" "Y233"    "Y248"    "Y268"    "BB002"   "BB020"   "BB032"  
[11] "BB044"   "BB056"   "Y234"    "Y249"    "Y271"    "BB003"   "BB021"   "BB033"   "BB045"   "BB057"  
[21] "Y236"    "Y250"    "Y272"    "BB004"   "BB022"

Answer 4

可以使用 sprintf 和 gsub function.This 步骤来提取数值并更改其格式。

num=sprintf("%03d",as.numeric(gsub("[^[:digit:]]", "", x)))

下一步是粘贴已更改格式的数字

x=paste(gsub("[^[:alpha:]]", "", x),num,sep="")

在 r 中添加前导 0

Adding leading 0s in r

r

leading-zero