Message-ID: <f582ec27-7294-4a87-8f45-eb387fc9c918@gmail.com>
Date: 2023-10-18T15:08:36Z
From: Ben Bolker
Subject: Best way to test for numeric digits?
In-Reply-To: <6c4ac344-ddbe-4c3d-8ecd-c5a29657893d@syonic.eu>
There are some answers on Stack Overflow:
https://stackoverflow.com/questions/14984989/how-to-avoid-warning-when-introducing-nas-by-coercion
On 2023-10-18 10:59 a.m., Leonard Mada via R-help 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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