r-根据值的长度在值的开头添加一个数字

Question

根据以下数据，如果值的长度小于9，我如何告诉R在值(列key(的开头添加0？

样本数据：

id = c(1,2,3,4,5,6,7,8,9,10)
Key = c("10032012", "10812012", "2073017", "10692013", "10892012", "10952014", "10972012", "560392013", "560372013", "56022012")
df = data.frame(id, Key)

期望输出：

df_desired = structure(list(id = c(1, 2, 3, 4, 5, 6, 7, 8, 9, 10), Key = c("010032012", 
"010812012", "02073017", "010692013", "010892012", "010952014", "010972012", 
"560392013", "560372013", "56022012")), class = "data.frame", row.names = c(NA, 
-10L))

Answer 1

一些答案对于任何字符串：

df$Key <- ifelse(nchar(df$Key) < 9, paste0("0", df$Key), df$Key)

如果它们都是整数字符串，则规范的方法是：

df$Key <- sprintf("%09d", as.integer(df$Key)) 

使用CCD_ 5&stringr

library(dplyr)
library(stringr)
df_desired <- df %>% mutate(Key = str_pad(Key, width = 9, pad = "0"))