使用R添加前导零 [英] Adding leading zeros using R

问题描述

  anim <-c（25499,25500,25501）我有一组数据，看起来像这样： ，25502,25503,25504）
 sex <-c（1,2,2,1,2,1）
 wt <-c（0.8,1.2,1.0,2.0,1.8,1.4 ）
 data < -  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 
  
 
 
 
我想在每个动物ID之前添加一个零： 
 
 
  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 
  
感兴趣的缘故，如果我需要在动物身份证之前添加两三个零呢？     简短的版本：use   formatC  或  sprintf  。
 
 
 
 
 
更长的版本：
 
 
格式化数字有几个功能，包括添加前导零。哪一个是最好的取决于你想要做的其他格式。
 
 
 
这个问题的例子很容易，因为所有的值都有相同的位数，所以我们来尝试一个比较宽泛的例子：
 
 
  anim<  -  25499：25504 
x < -  10 ^（0：5）
  
 
 
 
 
 
 
   粘贴  （它的变体 paste0 ）通常是你遇到的第一个字符串操作函数。它们并不是真正用于操纵数字的，但是可以用于这个目的。在这种简单的情况下，我们总是需要预先设置一个零， paste0 是最好的解决方案。 
 
 
  paste0（0，anim）
 ## [1]025499025500025501025502025503025504
  
 
 $ b 
对于数字中可变数字位数的情况，您必须手动计算需要多少个零，这太可怕了你应该只是出于病态的好奇心才行。 
 
 
 
 
 
    str_pad   来自 stringr 与 paste 的工作方式类似，使得它更加明确地表明你想要做的事情。
  library（stringr）
 str_pad（anim，6，pad =0）
 ## [1]025499025500025501025502 025503025504
  
同样，它不是真正用于数字的，所以更难的情况下需要一点思考。 
  str_pad（x）这个输出可以是零到宽8 ，8，pad =0）
 ## [1]00000001000000100000010000001000000100000001e + 05
  / pre> 
 
 
您需要设定科学罚款选项，这样数字总是使用固定的符号（而不是科学记数法）格式化。 
 
 
  library（ withr）
 with_options（
c（scipen = 999），
 str_pad（x，8，pad =0）
）
 ## [1]00000001 0000001000000100000010000001000000100000
  
 
 
 
 
 
 
    stri_pad  stringi 的工作原理与 str_pad 完全一样。 > stringr 。
 
 
 
 
 
 
    formatC   是C函数的一个接口。  printf  。使用它需要一些关于这个潜在功能的神秘的知识（见链接）。在这种情况下，重要的是宽度参数，格式是d代表整数，而0 标记用于预置零。 > 
 
 
  formatC（anim，width = 6，format =d，flag =0）
 ## [1] 025499025500025501025502025503025504
 formatC（x，width = 8，format =d，flag =0）
 ## [1 ]000000010000001000000100000010000001000000100000
  
这是我最喜欢的解决方案，因为它很容易修改宽度，而且功能足够强大，可以进行其他格式更改。
 
 
 
 
 
 
    sprintf   是同名的C函数的接口;例如 formatC ，但使用不同的语法。 
  sprintf（％06d，anim）
 ## [1]025499025500025501 025502025503025504
 sprintf（％08d，x）
 ## [1]000000010000001000000100000010000001000000100000 
  
  sprintf 的主要优点在于你可以将格式化的数字嵌入较长的文本内。
  sprintf（
动物ID％06d是％s。 ，
 anim，
 sample（c（lion，tiger），length（anim），replace = TRUE）
）
 ## [1] ID 025499是一只老虎。 动物ID 025500是一只老虎。 
 ## [3]动物ID 025501是狮子。 动物ID 025502是一只老虎。 
 ## [5]动物ID 025503是一只老虎。 动物ID 025504是一只狮子。 
  
另见 goodside's answer 。
 
 
 
 
为了完整起见，值得一提的是其他格式化函数偶尔有用，但是没有预先置零的方法。
 
 
 
    format   ，一种通用函数，用于格式化任何类型的对象，并使用数字方法。它有点像 formatC ，但有另一个接口。 
 
 
    prettyNum   是另一种格式功能，主要用于创建手动轴刻度标签。它适用于广泛的数字。
 
 
 
  scale  包有几个功能，例如  percent   ，  date_format  和<对于专业格式类型，  dollar   。
 
I have a set of data which looks something like this:
anim <- c(25499,25500,25501,25502,25503,25504)
sex  <- c(1,2,2,1,2,1)
wt   <- c(0.8,1.2,1.0,2.0,1.8,1.4)
data <- 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?
解决方案
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 <- 25499:25504
x <- 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.

                        
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