How to select rows in a column and add a zero to selected rows

Question

[Phylicia]

Hello! I have already written a code for this question, but my code is very complex. I want to enquiry, is there any simpler way to achieve the same goal. Thanks a lot!

Background: There is a column named id, in which there are 5 digit numbers and 6 digit numbers.

Aim: I want to select 5 digit numbers and add a zero in front of them and merge added-0 items with the original 6 digit numbers.

df is the name of the data frame.

#Select the columns whose ID digit is only 5 and add 0 in front of it.
df1 <- subset(df, nchar(as.character(df$id)) == 5)

df1 <- df1 %>% mutate("NewID"= paste0("0", df1$id))

#Select the columns whose ID digit is only 6 and merge it with the first subset
df2 <- subset(df, nchar(as.character(df$id)) == 6)

df2 <- df2 %>% mutate("NewID"= df2$id)
#Merge them
df3 <- rbind(df1, df2)

Answer 1

[rpolicastro]

Example data.

df <- data.frame(id=c(12345, 123456), val=1:2)

> df
      id val
1  12345   1
2 123456   2

Using sprintf from base R.

df$id <- sprintf("%06d", df$id)

With the str_pad function from stringr.

df <- mutate(df, id=str_pad(id, 6, "left", 0))

Result of either method.

> df
      id val
1 012345   1
2 123456   2

[cpad0112]

a typo or copy/paste issue in this line df <- mutate(df, id=str_pad(id, 6, "left")). In addition, for long numbers, user must set scipen so that number is not turned to e notation, with str_pad. str_pad has some weird behavior (from user point of view, if scipen is not set)

> str_pad(10000,8, "right", pad=0)
[1] "10000000"
> str_pad(100000, 7, "right", pad=0)
[1] "1e+0500"
> str_pad(1234000000, 7, "right", pad=0)
[1] "1.234e+09"

[rpolicastro]

a typo or copy/paste issue in this line df <- mutate(df, id=str_pad(id, 6, "left"))

Forgot to add 0 padding to it, thanks for pointing it out!

[Phylicia]

Thanks a lot for your kind help！

Answer 2

[erwan.scaon]

Hello,

# Packages
library(magrittr)
library(dplyr)

# Dummy data
test <- data.frame(
  id = c(12345, 123456, 54321, 654321),
  stuff = LETTERS[1:4]
)

> test
      id stuff
1  12345     A
2 123456     B
3  54321     C
4 654321     D

# Mutate the "id" column
# If less than 6 digits, return "suffix + id", else return "id"
test %<>%
  mutate(id = ifelse(nchar(id) < 6, paste0(0, id), id))

> test
      id stuff
1 012345     A
2 123456     B
3 054321     C
4 654321     D

[Phylicia]

Thanks a lot for your kind help！