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I have a series of column names that I'm trying to standardize.
names <- c("apple", "banana", "orange", "apple1", "apple2", "apple10", "apple11", "banana2", "banana12")
I would like anything that has a one digit number to be padded by a zero, so
apple
banana
orange
apple01
apple02
apple10
apple11
banana02
...
I've been trying to use stringr
strdouble <- str_detect(names, "[0-9]{2}")
strsingle <- str_detect(names, "[0-9]")
str_detect(names[strsingle & !strdouble])
but unable to figure out how to selectively replace/prepend...
932
The easiest way to put leading zeros before text strings in Excel is using the RIGHT function: "0000" is the maximum number of zeros you want to add. For example, to add 2 zeros, you type "00". Cell is a reference to the cell containing the original value. String_length is how many characters the resulting string should contain.
For example, to add leading zeros to create a 5-digit number, use the following format code: 00000. By using Excel custom numbers formats, you can add leading zeros to create fixed-length numbers, like in the above example, and variable-length numbers.
You can use the following syntax to add leading zeros to strings in a pandas DataFrame: This particular formula adds as many leading zeros as necessary to the strings in the column titled ‘ID’ until each string has a length of 7. Feel free to replace the 7 with another value to add a different number of leading zeros.
As shown in the screenshot below, the formula adds just one leading zero to all cells in a column regardless of how many characters the original value contains: In the same manner, you can insert 2 leading zeros (00), 3 zeros (000) or as many zeros as you want before numbers and text strings.
You can use sub("([a-z])([0-9])$","\\10\\2",names) :
[1] "apple" "banana" "orange" "apple01" "apple02" "apple10" "apple11" "banana02"
[9] "banana12"
It only changes the names where there is a single digit following a letter (the $ is the end of the string).
The \\1 selects the first block in () : the letter. Then it puts a leading 0, then the second block in () : the digit.
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