Bug 17988 - nlme::getGroupsFormula on corARMA gives 'form' argument must be a formula

[hturner]

In the discussion of Bug 17988, R Core member @mmaechler proposes two actions:

1. Abolish corIndent() objects
2. Give an error when corARMA(*) is called with p=q=0

The first of these has been implemented: corIdent() is deprecated in nlme version 3.1-162 (see entry dated 2023-01-28, https://svn.r-project.org/R-packages/trunk/nlme/ChangeLog). The second has not yet been implemented.

So we could create a patch implementing the second change:

• Update nlme::corARMA() (in nlme/R/corStruct.R)
• Update the help page: nlme/man/corARMA.Rd
• Run R CMD check on nlme with the updates
• Create a patch and share it on the original bug report

Note that nlme is maintained in Subversion: https://svn.r-project.org/R-packages/trunk/nlme, so you will need Subversion installed to check out the repo and create a patch.

[thomaszwagerman]

In corStruct.R, changed corARMA() warning if p + q == 0, added a warning message to replace deprecated corIdent() return:

  if (0 == (p + q)) {
    stop("at least one of p and q should be > 0. Use 'corAR1(0, *)' instead.")
  }

In help file corARMA.Rd, changed p & q item to:

 \item{p, q}{non-negative integers specifying respectively the
   autoregressive order and the moving average order of the \code{ARMA}
   structure. Both default to 0, but at least one should be > 0.}

[thomaszwagerman]

Updated error message to all lowercase and adding single quotes to parameters, consistent with error messages in the package

  if (0 == (p + q)) {
    stop("at least one of 'p' and 'q' should be > 0, use 'corAR1(0, *)' instead")
  }

[thomaszwagerman]

patch.diff submitted to the bug report

[hturner]

This bug is now CLOSED FIXED 🎉