[R] effects() extractor for a quantile reqression object: error message

[Martin Maechler]

>>>>> Christopher W Ryan via R-help 
>>>>>     on Thu, 5 Sep 2024 22:50:24 -0400 writes:

    > I'm using quantreg package version 5.98 of 24 May 2024, in R 4.4.1 on
    > Linux Mint.

    > The online documentation for quantreg says, in part, under the
    > description of the rq.object, "The coefficients, residuals, and effects
    > may be extracted by the generic functions of the same name, rather than
    > by the $ operator."

    > I create an rq object for the 0.9 quantile, called qm.9

    > effects(qm.9)

    > yields, the error message, " effects(qm.9)
    > Error in UseMethod("effects") :
    > no applicable method for 'effects' applied to an object of class "rq"

    > I'm confused. Appreciate any suggestions. Thanks.

    > --Chris Ryan

Unfortunately, the documentation is wrong, here.

You can always use

     methods(class = class(qm.9))

to get list of generic function names for there is a method for
your object (of class "rq") in this case...
and indeed, "effects" is not among them.

Possibly this was a thinko (on the 'rq.object' help page) and
it was "predict" that was meant there,
as indeed there is a predict method (actually there are even 3
different predict() methods in package 'quantreg', and they are
well documented on the  ?predict.qr  help page.

{OTOH my guess is that there originally *was* an effects method
 and it has been dropped in the mean time}


Martin Maechler

ETH Zurich  and  R Core team