How to change values before text in string using R-CodePudding

I have multiple strings that are similar to the following pattern:

dat<-("00000000AAAAAAAAAA0AAAAAAAAAA0AAAAAAAAAAAAAAAAAAAAAAAAD0")

I need to change all 0 values to "." before the first character value within a string. My desired output in this example would be:

"........AAAAAAAAAA0AAAAAAAAAA0AAAAAAAAAAAAAAAAAAAAAAAAD0".

I tried using gsub to accomplish this task:

gsub("\\G([^_\\d]*)\\d", ".\\1", dat, perl=T)

Unfortunately it changed all of the 0s to "." instead of the 0s preceding the first "A".

Can someone please help me with this issue?

CodePudding user response：

If you wish to simply replace each leading 0 with a ., you can use

gsub("\\G0", ".", dat, perl=TRUE)

Here, \G0 matches a 0 char at the start of string, and then every time after a successful match. See this regex demo.

If you need to replace each 0 in a string before the first letter you can use

gsub("\\G[^\\p{L}0]*\\K0", ".", dat, perl=TRUE)

Here, \G matches start of string or end of the preceding successful match, [^\p{L}0]* matches zero or more chars other than a letter and 0, then \K omits the matched text, and then 0 matches the 0 char and it is replaced with a .. See this regex demo.

See the R demo online:

dat <- c("00000000AAAAAAAAAA0AAAAAAAAAA0AAAAAAAAAAAAAAAAAAAAAAAAD0","102030405000AZD")
gsub("\\G0", ".", dat, perl=TRUE)
## [1] "........AAAAAAAAAA0AAAAAAAAAA0AAAAAAAAAAAAAAAAAAAAAAAAD0"
## [2] "102030405000AZD"                                         
gsub("\\G[^\\p{L}0]*\\K0", ".", dat, perl=TRUE)
## [1] "........AAAAAAAAAA0AAAAAAAAAA0AAAAAAAAAAAAAAAAAAAAAAAAD0"
## [2] "1.2.3.4.5...AZD"

CodePudding user response：

This is really hard. So I tried to do it with a custom function:

library(stringr)

dat<-("00000000AAAAAAAAAA0AAAAAAAAAA0AAAAAAAAAAAAAAAAAAAAAAAAD0")

Zero_Replacer <- function(x) {
  x <- str_split(x, '[A-Za-z]', 2)
  x[[1]][1] <- str_replace_all(x[[1]][1], "0", ".")
  paste0(x[[1]][1], x[[1]][2])
}

Zero_Replacer(dat)

Output:

[1] "........AAAAAAAAA0AAAAAAAAAA0AAAAAAAAAAAAAAAAAAAAAAAAD0"