[R] Best way to test for numeric digits?

[Leonard Mada]

Dear Rui,

On 10/18/2023 8:45 PM, Rui Barradas wrote:
> split_chem_elements <- function(x, rm.digits = TRUE) {
>   regex <- "(?<=[A-Z])(?![a-z]|$)|(?<=.)(?=[A-Z])|(?<=[a-z])(?=[^a-z])"
>   if(rm.digits) {
>     stringr::str_replace_all(mol, regex, "#") |>
>       strsplit("#|[[:digit:]]") |>
>       lapply(\(x) x[nchar(x) > 0L])
>   } else {
>     strsplit(x, regex, perl = TRUE)
>   }
> }
>
> split.symbol.character = function(x, rm.digits = TRUE) {
>   # Perl is partly broken in R 4.3, but this works:
>   regex <- "(?<=[A-Z])(?![a-z]|$)|(?<=.)(?=[A-Z])|(?<=[a-z])(?=[^a-z])"
>   s <- strsplit(x, regex, perl = TRUE)
>   if(rm.digits) {
>     s <- lapply(s, \(x) x[grep("[[:digit:]]+", x, invert = TRUE)])
>   }
>   s
> }

You have a glitch (mol is hardcoded) in the code of the first function. 
The times are similar, after correcting for that glitch.

Note:
- grep("[[:digit:]]", ...) behaves almost twice as slow as grep("[0-9]", 
...)!
- corrected results below;

Sincerely,

Leonard
#######

split_chem_elements <- function(x, rm.digits = TRUE) {
   regex <- "(?<=[A-Z])(?![a-z]|$)|(?<=.)(?=[A-Z])|(?<=[a-z])(?=[^a-z])"
   if(rm.digits) {
     stringr::str_replace_all(x, regex, "#") |>
       strsplit("#|[[:digit:]]") |>
       lapply(\(x) x[nchar(x) > 0L])
   } else {
     strsplit(x, regex, perl = TRUE)
   }
}

split.symbol.character = function(x, rm.digits = TRUE) {
   # Perl is partly broken in R 4.3, but this works:
   regex <- "(?<=[A-Z])(?![a-z]|$)|(?<=.)(?=[A-Z])|(?<=[a-z])(?=[^a-z])"
   s <- strsplit(x, regex, perl = TRUE)
   if(rm.digits) {
     s <- lapply(s, \(x) x[grep("[0-9]", x, invert = TRUE)])
   }
   s
}

mol <- c("CCl3F", "Li4Al4H16", "CCl2CO2AlPO4SiO4Cl")
mol10000 <- rep(mol, 10000)

system.time(
   split_chem_elements(mol10000)
)
#   user  system elapsed
#   0.58    0.00    0.58

system.time(
   split.symbol.character(mol10000)
)
#   user  system elapsed
#   0.67    0.00    0.67