R help - Nov 2011 - proper work-flow with 'formula' objects and lm()

Dear all
I have a work-flow issue with lm(). When I use
> lm(y1~x1, anscombe)
Call:
lm(formula = y1 ~ x1, data = anscombe)

Coefficients:
(Intercept)           x1
     3.0001       0.5001


I get as expected the formula, "y1 ~ x1", in the print()ed results or
summary(). However, if I pass through a formula object
> (form <- formula(y1~x1))
y1 ~ x1
> lm(form, anscombe)
Call:
lm(formula = form, data = anscombe)

Coefficients:
(Intercept)           x1
     3.0001       0.5001


then I only get the object name in the call, 'form', instead of the
formula. When passing a 'formula' object to lm, is it possible to
retain in the resulting 'lm' object the actual formula used for the
regression: "y1 ~ x1"?

Regards
Liviu


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On 24/11/2011 2:48 PM, Liviu Andronic wrote:
> Dear all
> I have a work-flow issue with lm(). When I use
> >  lm(y1~x1, anscombe)
>
> Call:
> lm(formula = y1 ~ x1, data = anscombe)
>
> Coefficients:
> (Intercept)           x1
>       3.0001       0.5001
>
>
> I get as expected the formula, "y1 ~ x1", in the print()ed
results or
> summary(). However, if I pass through a formula object
> >  (form<- formula(y1~x1))
> y1 ~ x1
> >  lm(form, anscombe)
>
> Call:
> lm(formula = form, data = anscombe)
>
> Coefficients:
> (Intercept)           x1
>       3.0001       0.5001
>
>
> then I only get the object name in the call, 'form', instead of the
> formula. When passing a 'formula' object to lm, is it possible to
> retain in the resulting 'lm' object the actual formula used for the
> regression: "y1 ~ x1"?
It is retained.  terms(fit) will give it to you, if fit is an lm object.

Duncan Murdoch

On Thu, Nov 24, 2011 at 2:48 PM, Liviu Andronic <landronimirc at
gmail.com> wrote:
> Dear all
> I have a work-flow issue with lm(). When I use
>> lm(y1~x1, anscombe)
>
> Call:
> lm(formula = y1 ~ x1, data = anscombe)
>
> Coefficients:
> (Intercept) ? ? ? ? ? x1
> ? ? 3.0001 ? ? ? 0.5001
>
>
> I get as expected the formula, "y1 ~ x1", in the print()ed
results or
> summary(). However, if I pass through a formula object
>> (form <- formula(y1~x1))
> y1 ~ x1
>> lm(form, anscombe)
>
> Call:
> lm(formula = form, data = anscombe)
>
> Coefficients:
> (Intercept) ? ? ? ? ? x1
> ? ? 3.0001 ? ? ? 0.5001
>
>
> then I only get the object name in the call, 'form', instead of the
> formula. When passing a 'formula' object to lm, is it possible to
> retain in the resulting 'lm' object the actual formula used for the
> regression: "y1 ~ x1"?
>
Try this:
> form <- formula(y1~x1)
> do.call("lm", list(form, quote(anscombe)))
Call:
lm(formula = y1 ~ x1, data = anscombe)

Coefficients:
(Intercept)           x1
     3.0001       0.5001

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