R help - Sep 2024 - effects() extractor for a quantile reqression object: error message

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

>>>>> 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