[R] regexpr: R takes very long with non-existent pattern

[Bert Gunter]

Doubt that I can help, but what does "not defined" mean? -- NA, "", " " ?
Something else?
I would guess that if it's NA, you should get an immediate error.
If it's "" , that's a legitimate pattern and would result in matches of 0
length for everything, which might trigger an error in other parts of your
code.
All a guess, though.

Bert Gunter

"The trouble with having an open mind is that people keep coming along and
sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )


On Wed, May 18, 2022 at 5:08 PM Leonard Mada via R-help <
r-help using r-project.org> wrote:

> Dear R Users,
>
>
> I have run the following command in R:
>
> # x = larger vector of strings (1200 Pubmed abstracts);
> # patt = not defined;
> npos = regexpr(patt, x, perl=TRUE);
> # Error in regexpr(patt, x, perl = TRUE) : object 'patt' not found
>
>
> The problem:
>
> R becomes unresponsive and it takes 1-2 minutes to return the error. The
> operation completes almost instantaneously with a valid pattern.
>
> Is there a reason for this behavior?
>
> Tested with R 4.2.0 on MS Windows 10.
>
>
> I have uploaded a set with 1200 Pubmed abstracts on Github, if anyone
> wants to check:
>
> - see file: Example_Abstracts_Title_Pubmed.csv;
>
> https://github.com/discoleo/R/tree/master/TextMining/Pubmed
>
> The variable patt was not defined due to an error: but it took very long
> to exit the operation and report the error.
>
>
> Many thanks,
>
>
> Leonard
>
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