[R] Best way to test for numeric digits?

[Jeff Newmiller]

Use any occurrence of one or more digits as a separator?

s <- c( "CCl3F", "Li4Al4H16", "CCl2CO2AlPO4SiO4Cl" )
strsplit( s, "\\d+" )


On October 18, 2023 7:59:01 AM PDT, Leonard Mada via R-help <r-help using r-project.org> wrote:
>Dear List members,
>
>What is the best way to test for numeric digits?
>
>suppressWarnings(as.double(c("Li", "Na", "K",  "2", "Rb", "Ca", "3")))
># [1] NA NA NA  2 NA NA  3
>The above requires the use of the suppressWarnings function. Are there any better ways?
>
>I was working to extract chemical elements from a formula, something like this:
>split.symbol.character = function(x, rm.digits = TRUE) {
>    # Perl is partly broken in R 4.3, but this works:
>    regex = "(?<=[A-Z])(?![a-z]|$)|(?<=.)(?=[A-Z])|(?<=[a-z])(?=[^a-z])";
>    # stringi::stri_split(x, regex = regex);
>    s = strsplit(x, regex, perl = TRUE);
>    if(rm.digits) {
>        s = lapply(s, function(s) {
>            isNotD = is.na(suppressWarnings(as.numeric(s)));
>            s = s[isNotD];
>        });
>    }
>    return(s);
>}
>
>split.symbol.character(c("CCl3F", "Li4Al4H16", "CCl2CO2AlPO4SiO4Cl"))
>
>
>Sincerely,
>
>
>Leonard
>
>
>Note:
># works:
>regex = "(?<=[A-Z])(?![a-z]|$)|(?<=.)(?=[A-Z])|(?<=[a-z])(?=[^a-z])";
>strsplit(c("CCl3F", "Li4Al4H16", "CCl2CO2AlPO4SiO4Cl"), regex, perl = T)
>
>
># broken in R 4.3.1
># only slightly "erroneous" with stringi::stri_split
>regex = "(?<=[A-Z])(?![a-z]|$)|(?=[A-Z])|(?<=[a-z])(?=[^a-z])";
>strsplit(c("CCl3F", "Li4Al4H16", "CCl2CO2AlPO4SiO4Cl"), regex, perl = T)
>
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-- 
Sent from my phone. Please excuse my brevity.