R help - Jun 2011 - What does class "call" mean? How do I make class "formula" into a "call"?

I have a list called "tabs" that I would like to have the same
structure as my list "eqSystem." The two look like they have the same
format but they are different because when I look at their attributes,
class(eqSystem[[1]]) is "call" but class(tabs[[1]]) is
"formula". I want to have class(tabs[[1]]) as a call too. So what does
"call" mean? And how do I make an object of type "formula"
be of type "call"??
Thank you so much!!!--Rita
> class(tabs)
[1] "list"
> class(tabs[1])
[1] "list"
> class(tabs[[1]])
[1] "formula"> class(eqSystem)
[1] "list"
> class(eqSystem[1])
[1] "list"
> class(eqSystem[[1]])
[1] "call"


Rita
===================================="If you think education is expensive,
try ignorance."--Derek Bok

Hello R Users! 
I have a list called "tabs" that I would like to have the same
structure as
my list "eqSystem." The two look like they have the same structure but
they
are different because when I look at their attributes, class(eqSystem[[1]])
is "call" but class(tabs[[1]]) is "formula". I want to have
class(tabs[[1]])
as a call too. 

So what does "call" mean? 

And how do I make an object of class "formula" be of class
"call"?
Thank you so much!!!--Rita

> class(tabs)
[1] "list"
> class(tabs[1])
[1] "list"
> class(tabs[[1]])
[1] "formula"> class(eqSystem)
[1] "list"
> class(eqSystem[1])
[1] "list"
> class(eqSystem[[1]])
[1] "call"

Rita
===================================="If you think education is expensive,
try ignorance."--Derek Bok

--
View this message in context:
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Sent from the R help mailing list archive at Nabble.com.

Well, this is kind of complicated. The first place you should go for
help is not this list, but the R docs. Specfically ?call.  This
assumes familiarity with R's (S3) class system and language structure,
however.. For this, I suggest ?UseMethod and consulting the R Language
Definition Manual.

Perhaps some brave soul on this list will attempt a short explanation
in reply. But I am not (s)he.

Cheers,
Bert

Oh -- as for specific suggestions, I think you need to do what the
posting guide asks and provide a minimal reproducible example to give
people a clearer idea of what's going on.

On Fri, Jun 24, 2011 at 2:58 PM, Rita Carreira <ritacarreira at
hotmail.com> wrote:
>
> I have a list called "tabs" that I would like to have the same
structure as my list "eqSystem." The two look like they have the same
format but they are different because when I look at their attributes,
class(eqSystem[[1]]) is "call" but class(tabs[[1]]) is
"formula". I want to have class(tabs[[1]]) as a call too. So what does
"call" mean? And how do I make an object of type "formula"
be of type "call"?
> Thank you so much!!!--Rita
>> class(tabs)
> [1] "list"
>> class(tabs[1])
> [1] "list"
>> class(tabs[[1]])
> [1] "formula"> class(eqSystem)
> [1] "list"
>> class(eqSystem[1])
> [1] "list"
>> class(eqSystem[[1]])
> [1] "call"
>
>
> Rita
> ====================================> "If you think education is
expensive, try ignorance."--Derek Bok
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>


-- 
"Men by nature long to get on to the ultimate truths, and will often
be impatient with elementary studies or fight shy of them. If it were
possible to reach the ultimate truths without the elementary studies
usually prefixed to them, these would not be preparatory studies but
superfluous diversions."

-- Maimonides (1135-1204)

Bert Gunter
Genentech Nonclinical Biostatistics

On Jun 24, 2011, at 6:12 PM, StellathePug wrote:
> Hello R Users!
> I have a list called "tabs" that I would like to have the same  
> structure as
> my list "eqSystem." The two look like they have the same
structure
> but they
> are different because when I look at their attributes,  
> class(eqSystem[[1]])
> is "call" but class(tabs[[1]]) is "formula". I want to
have
> class(tabs[[1]])
> as a call too.
>
> So what does "call" mean?
An as yet unevaluated function invocation with first as the named  
function followed by quoted arguments is a "call":

See the help(call) page:

 > f <- round
 > A <- 10.5
 > (g <- as.call(list(f, quote(A))))
.Primitive("round")(A)
 > eval(g)
[1] 10

 > call("mean", quote( c(1,2,3)))
mean(c(1, 2, 3))
 > eval( call("mean", quote( c(1,2,3))))
[1] 2

It seems very unlikely that a formula object could be coerced into a  
valid call simply by altering its class. To convince us otherwise you  
need to provide more information than you have supplied to the  
present. The results of str() on these objects might be a first step.

-- 
David.
>
> And how do I make an object of class "formula" be of class
"call"?
> Thank you so much!!!--Rita
>
>
>> class(tabs)
> [1] "list"
>> class(tabs[1])
> [1] "list"
>> class(tabs[[1]])
> [1] "formula"> class(eqSystem)
> [1] "list"
>> class(eqSystem[1])
> [1] "list"
>> class(eqSystem[[1]])
> [1] "call"
>
> Rita
> ====================================> "If you think education is
expensive, try ignorance."--Derek Bok
>
> --
> View this message in context:
http://r.789695.n4.nabble.com/What-does-class-call-mean-How-do-I-make-class-formula-into-a-call-tp3623733p3623733.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
David Winsemius, MD
West Hartford, CT

Thank you Bert and Prof. Ripley for your feedback. I did read the language
documentation and it was not entirely clear to me, but I'm one of those
people that has to read and digest something before it clicks. However, I did
realize that the issue with "call"and "formula" was not the
real reason why my program did not work. The real reason was much more trivial:
I put the arguments inside the systemfit function out of order. Eventually, I
figured it out. The good thing about this is that I learned about the existence
of the R language documentation.?
Thank you again both!
Rita
===================================="If you think education is expensive,
try ignorance."--Derek Bok


----------------------------------------
> Date: Sat, 25 Jun 2011 05:59:40 +0100
> From: ripley at stats.ox.ac.uk
> To: gunter.berton at gene.com
> CC: ritacarreira at hotmail.com
> Subject: Re: [R] What does class "call" mean? How do I make class
"formula" into a "call"?
>
> This is really a misleading subject: it is already a call! From
> ?class
>
> Many R objects have a ?class? attribute, a character vector giving
> the names of the classes from which the object _inherits_. If the
> object does not have a class attribute, it has an implicit class,
> ?"matrix"?, ?"array"? or the result of ?mode(x)?
(except that
> integer vectors have implicit class ?"integer"?).
>
> So, simply remove the class if you want the mode: but anything which
> needs to know this is call will be looking at the mode and not the
> class.
>
> > zz <- ~x
> > class(zz)
> [1] "formula"
> > mode(zz)
> [1] "call"
>
> And see ?mode and ?call. Formulae and calls which are not formulae
> are completely different: you cannot coerce one to the other.
>
>
> On Fri, 24 Jun 2011, Bert Gunter wrote:
>
> > Well, this is kind of complicated. The first place you should go for
> > help is not this list, but the R docs. Specfically ?call. This
> > assumes familiarity with R's (S3) class system and language
structure,
> > however.. For this, I suggest ?UseMethod and consulting the R Language
> > Definition Manual.
> >
> > Perhaps some brave soul on this list will attempt a short explanation
> > in reply. But I am not (s)he.
> >
> > Cheers,
> > Bert
> >
> > Oh -- as for specific suggestions, I think you need to do what the
> > posting guide asks and provide a minimal reproducible example to give
> > people a clearer idea of what's going on.
> >
> > On Fri, Jun 24, 2011 at 2:58 PM, Rita Carreira <ritacarreira at
hotmail.com> wrote:
> >>
> >> I have a list called "tabs" that I would like to have
the same
> >> structure as my list "eqSystem." The two look like they
have the
> >> same format but they are different because when I look at their
> >> attributes, class(eqSystem[[1]]) is "call" but
class(tabs[[1]]) is
> >> "formula". I want to have class(tabs[[1]]) as a call
too. So what
> >> does "call" mean? And how do I make an object of type
"formula" be
> >> of type "call"?
> >> Thank you so much!!!--Rita
> >>> class(tabs)
> >> [1] "list"
> >>> class(tabs[1])
> >> [1] "list"
> >>> class(tabs[[1]])
> >> [1] "formula"> class(eqSystem)
> >> [1] "list"
> >>> class(eqSystem[1])
> >> [1] "list"
> >>> class(eqSystem[[1]])
> >> [1] "call"
> >>
> >>
> >> Rita
> >> ====================================> >> "If you
think education is expensive, try ignorance."--Derek Bok
> >>
> >> ______________________________________________
> >> R-help at r-project.org mailing list
> >> https://stat.ethz.ch/mailman/listinfo/r-help
> >> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> >> and provide commented, minimal, self-contained, reproducible code.
> >>
> >
> >
> >
> > --
> > "Men by nature long to get on to the ultimate truths, and will
often
> > be impatient with elementary studies or fight shy of them. If it were
> > possible to reach the ultimate truths without the elementary studies
> > usually prefixed to them, these would not be preparatory studies but
> > superfluous diversions."
> >
> > -- Maimonides (1135-1204)
> >
> > Bert Gunter
> > Genentech Nonclinical Biostatistics
> >
> > ______________________________________________
> > R-help at r-project.org mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> > and provide commented, minimal, self-contained, reproducible code.
> >
>
> --
> Brian D. Ripley, ripley at stats.ox.ac.uk
> Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
> University of Oxford, Tel: +44 1865 272861 (self)
> 1 South Parks Road, +44 1865 272866 (PA)
> Oxford OX1 3TG, UK Fax: +44 1865 272595