How to add leading zeros

Question

I have a set of data which looks something like this   anim  lt - c 25499 25500 25501 25502 25503 25504  sex   lt - c 1 2 2 1 2 1  wt    lt - c 0 8 1 2 1 0 2 0 1 8 1 4  data  lt - data frame anim sex wt   data    anim sex  wt anim2 1 25499   1 0 8     2 2 25500   2 1 2     2 3 25501   2 1 0     2 4 25502   1 2 0     2 5 25503   2 1 8     2 6 25504   1 1 4     2   I would like a zero to be added before each animal id   data    anim sex  wt anim2 1 025499   1 0 8     2 2 025500   2 1 2     2 3 025501   2 1 0     2 4 025502   1 2 0     2 5 025503   2 1 8     2 6 025504   1 1 4     2   And for interest sake  what if I need to add two or three zeros before the animal id s

User · Answer

data anim  lt - sapply 0  paste0 data anim

User · Answer

The short version  use formatC or sprintf     The longer version   There are several functions available for formatting numbers  including adding leading zeroes   Which one is best depends upon what other formatting you want to do   The example from the question is quite easy since all the values have the same number of digits to begin with  so let s try a harder example of making powers of 10 width 8 too   anim  lt - 25499 25504 x  lt - 10    0 5      paste  and it s variant paste0  are often the first string manipulation functions that you come across   They aren t really designed for manipulating numbers  but they can be used for that   In the simple case where we always have to prepend a single zero  paste0 is the best solution   paste0  0   anim      1   025499   025500   025501   025502   025503   025504    For the case where there are a variable number of digits in the numbers  you have to manually calculate how many zeroes to prepend  which is horrible enough that you should only do it out of morbid curiosity     str pad from stringr works similarly to paste  making it more explicit that you want to pad things   library stringr  str pad anim  6  pad    0       1   025499   025500   025501   025502   025503   025504    Again  it isn t really designed for use with numbers  so the harder case requires a little thinking about   We ought to just be able to say  pad with zeroes to width 8   but look at this output   str pad x  8  pad    0       1   00000001   00000010   00000100   00001000   00010000   0001e 05    You need to set the scientific penalty option so that numbers are always formatted using fixed notation  rather than scientific notation    library withr  with options    c scipen   999      str pad x  8  pad    0         1   00000001   00000010   00000100   00001000   00010000   00100000      stri pad in stringi works exactly like str pad from stringr     formatC is an interface to the C function printf   Using it requires some knowledge of the arcana of that underlying function  see link    In this case  the important points are the width argument  format being  d  for  integer   and a  0  flag for prepending zeroes   formatC anim  width   6  format    d   flag    0       1   025499   025500   025501   025502   025503   025504  formatC x  width   8  format    d   flag    0       1   00000001   00000010   00000100   00001000   00010000   00100000    This is my favourite solution  since it is easy to tinker with changing the width  and the function is powerful enough to make other formatting changes     sprintf is an interface to the C function of the same name  like formatC but with a different syntax     sprintf   06d   anim      1   025499   025500   025501   025502   025503   025504  sprintf   08d   x      1   00000001   00000010   00000100   00001000   00010000   00100000    The main advantage of sprintf is that you can embed formatted numbers inside longer bits of text   sprintf     Animal ID  06d was a  s       anim     sample c  lion    tiger    length anim   replace   TRUE        1   Animal ID 025499 was a tiger    Animal ID 025500 was a tiger       3   Animal ID 025501 was a lion     Animal ID 025502 was a tiger       5   Animal ID 025503 was a tiger    Animal ID 025504 was a lion      See also goodside s answer     For completeness it is worth mentioning the other formatting functions that are occasionally useful  but have no method of prepending zeroes   format  a generic function for formatting any kind of object  with a method for numbers   It works a little bit like formatC  but with yet another interface   prettyNum is yet another formatting function  mostly for creating manual axis tick labels   It works particularly well for wide ranges of numbers   The scales package has several functions such as percent  date format and dollar for specialist format types

User · Answer

Here is another alternative for adding leading to 0s to strings such as CUSIPs which can sometimes look like a number and which many applications such as Excel will corrupt and remove the leading 0s or convert them to scientific notation    When I tried the answer provided by  metasequoia the vector returned had leading spaces and not 0s  This was the same problem mentioned by  user1816679 -- and removing the quotes around the 0 or changing from  d to  s did not make a difference either  FYI  I am using RStudio Server running on an Ubuntu Server  This little two-step solution worked for me   gsub pattern        replacement    0   x   sprintf fmt     09s   ids  CUSIP     using the   gt   pipe function from the magrittr package it could look like this   sprintf fmt     09s   ids  CUSIP     gt   gsub pattern        replacement    0   x       I d prefer a one-function solution  but it works

User · Answer

Expanding on  goodside s repsonse   In some cases you may want to pad a string with zeros  e g  fips codes or other numeric-like factors   In OSX Linux    gt  sprintf   05s    104    1   00104    But because sprintf   calls the OS s C sprintf   command  discussed here  in Windows 7 you get a different result     gt  sprintf   05s    104    1     104    So on Windows machines the work around is    gt  sprintf   05d   as numeric  104     1   00104

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Here s a generalizable base R function   pad left  lt - function x  len   1   max nchar x    char    0         unlist lapply x  function x            paste0              paste rep char  len - nchar x    collapse                    x                      pad left 1 100    I like sprintf but it comes with caveats like      however the actual implementation will follow the C99 standard and fine details  especially the behaviour under user error  may depend on the platform

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For other circumstances in which you want the number string to be consistent  I made a function    Someone may find this useful   idnamer lt -function x y   Alphabetical designation and number of integers required     id lt -c 1 y      for  i in 1 length id             if nchar id i   lt 2               id i  lt -paste  0  id i  sep                          id lt -paste x id sep         return id    idnamer  EF  28    Sorry about the formatting

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str pad from the stringr package is an alternative   anim   25499 25504 str pad anim  width 6  pad  0

User · Answer

For a general solution that works regardless of how many digits are in data anim  use the sprintf function  It works like this   sprintf   04d   1     1   0001  sprintf   04d   104     1   0104  sprintf   010d   104     1   0000000104    In your case  you probably want  data anim  lt - sprintf   06d   data anim

[r] How to add leading zeros?

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