[R] Problem with object inside a function

[Ronaldo Reis Junior]

Em Dom 20 Abr 2008, Duncan Murdoch escreveu:
> On 20/04/2008 9:40 AM, Ronaldo Reis Junior wrote:
> > Hi all,
> >
> > I have a problem with an object inside a formula in a function that I
> > make.
> >
> > I create an object named qvartemp. This object is OK, look the levels:
> >> print(levels(qvartemp))
> >
> > [1] "baixomedio" "alto"
> >
> > Now I create a new object with a new formula:
> >> new.form <- as.formula(gsub(qvar,"qvartemp",as.expression(mma$formula)))
> >
> > Look this new object:
> >> print(new.form)
> >
> > Riqueza ~ Biomassa * qvartemp
> >
> > Now here is the problem, I try to update an existing model (mma) changing
> > the formula by the new.form
> >
> > mmaa <- update(mma,new.form)
> >
> > But my function is aborted with this message:
> >
> > Error in eval(expr, envir, enclos) : object "qvartemp" not found
> >
> > If I create this object qvartemp in R section manually it my function
> > work, because it get the object from my workspace (but it is usefull just
> > for testing), but my function dont find this object qvartemp created
> > inside the function.
> >
> > If I run all my function line by line without use the function it work, I
> > think that is because in this case the object is created in my workspace.
> > But when I run a function the object is created only in memory (not in my
> > workspece) and in this case update dont find this object.
> >
> > Anybody can suggest any Idea to fix it? I necessary I send my function
> > and a example.
>
> Formulas have attached environments; that's where they look for the
> variables they use.  You created new.form, but didn't give it the
> environment of the old one.
>
> I think all you need is
>
> environment(new.form) <- environment(mma$formula)
>
> Duncan Murdoch

Hi Duncan,

thanks for your quick reply. I think that is not the problem, because with glm 
or lm the formula inside the new.form work, only on update it dont work.

But I try this solution, I put new.form enclosed in an environment:

environment(new.form) <- 
environment(as.formula(gsub(qvar,"qvartemp",as.expression(mma$formula))))

But the error is the same.

Thanks
Ronaldo
-- 
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--
> Prof. Ronaldo Reis Júnior
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