R help - Jan 2007 - advice on semi-serious attempt to extend summary

Dear R wizards:

I am trying (finally) to build a function that might be useful to
others.  In particular, I want to create a summary.lme (extended lm)
method that [a] adds normalized coefficients and [b] white
heteroskedasticity adjusted se's and T's.  I believe I already know
how to do the programming to do these two, at least in simple
unweighted cases.  Now my challenges are just [1] to trap weird cases
(e.g., hccm dies because the standard errors cannot be computed), and
[2] to follow "proper R rules and regulations."

I started my experiments by copying summary.lm() to summary.lme.  But
there is some magic that I do not understand.  Apparently, the
  class(ans) <- "summary.lm"
signals to R that it should not produce an unlisted summary of the
components of ans, but that it should print something that is nicely
formatted.
  example:  y=rnorm(5); x=rnorm(5); m=lm(y~x);  summary.lm(m);
does exactly this nice output.  alas, just replacing the name at the end with
    class(ans) <- "summary.lme"
and typing summary.lme(m), having renamed summary.lm to summary, then
loses the nice printout.

so, it seems to me that somewhere R knows that a "summary.lm" object
gets special printing.  if I have not misunderstood this, then where
and how does this magic happen?

advice appreciated.

regards,

/iaw

Try:

methods(print)
stats:::print.summary.lm

On 1/1/07, ivo welch <ivowel at gmail.com> wrote:
> Dear R wizards:
>
> I am trying (finally) to build a function that might be useful to
> others.  In particular, I want to create a summary.lme (extended lm)
> method that [a] adds normalized coefficients and [b] white
> heteroskedasticity adjusted se's and T's.  I believe I already know
> how to do the programming to do these two, at least in simple
> unweighted cases.  Now my challenges are just [1] to trap weird cases
> (e.g., hccm dies because the standard errors cannot be computed), and
> [2] to follow "proper R rules and regulations."
>
> I started my experiments by copying summary.lm() to summary.lme.  But
> there is some magic that I do not understand.  Apparently, the
>  class(ans) <- "summary.lm"
> signals to R that it should not produce an unlisted summary of the
> components of ans, but that it should print something that is nicely
> formatted.
>  example:  y=rnorm(5); x=rnorm(5); m=lm(y~x);  summary.lm(m);
> does exactly this nice output.  alas, just replacing the name at the end
with
>    class(ans) <- "summary.lme"
> and typing summary.lme(m), having renamed summary.lm to summary, then
> loses the nice printout.
>
> so, it seems to me that somewhere R knows that a "summary.lm"
object
> gets special printing.  if I have not misunderstood this, then where
> and how does this magic happen?
>
> advice appreciated.
>
> regards,
>
> /iaw
>
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