[Rd] [PATCH] Three improvements to confint() documentation and S4 support

[Aakriti Kushwaha]

Hello R developers,


I would like to contribute three improvements to the R source:


   1.

   *S4 object support for **confint.default()*

   -

      confint.default() now works on S4 objects as long as suitable coef()
      and vcov() methods exist.

   2.

   *substring()** and **substr()** improvements*

   -

      Both functions now accept i2 = NULL, allowing extraction until the
      end of the string.
      -

      Improves convenience and aligns with user expectations.

   3.

   *Introduction of **%notin%** operator*

   -

      %notin% added as a base R idiom for !(x %in% table).
      -

      Enhances readability and avoids repeated negation in user code.



*Motivation:*


   -

   Enhance S4 object compatibility.
   -

   Improve string handling convenience.
   -

   Provide a cleaner syntax for common negation of %in%.


*Impact:*


   -

   Backward compatible; no breaking changes for existing S3 workflows.

   The corresponding patch files are attached to this email.

   I hope these changes are helpful. I look forward to any feedback or
   suggestions you may have.


   Thank you for your time and for maintaining R!


   Best regards,

   Aakriti Kushwaha

   GitHub: aakritixyz <https://github.com/aakritixyz>