Good night dear!
For years I have a problem that I have avoided with the use of the switch
function, but now I want to solve by following the good practices of object
orientation (OOP).
My function was created to generate experiments according to some input
parameters. Therefore, the first argument does not have a class defined as
"data.frame", "matrix", etc., so that from the generic,
specific methods can
be called.
I made a simple example to show my problem.
foo <- function (x, ...) UseMethod ('foo')
foo.default <- function(x,
a = 10,
b = NULL,
cc = 2,
dd = 3,
type = c ('brazil', 'argentina'),
...){
ty <- match.arg(type)
obj <- list(a = a,
b = b,
cc = cc,
dd = dd)
class (obj) <- paste ('foo',
ty,
sep = '.')
res <- foo(x = obj, ...)
}
foo.brazil <- function(x, ...){
a <- x$a
cc <- x$cc
res <- a + cc
return (res)
}
foo.argentina <- function(x, ...){
cc <- x$cc
dd <- x$dd
res <- sqrt(cc + dd)
return (res)
}
foo(a = 1)
If anyone has any light I thank them immensely.
--
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<<>>Prof. D.Sc. Ivan Bezerra Allaman
Laborat?rio de Estat?stica Computacional
Departamento de Ci?ncias Exatas e Tecnol?gicas
Universidade Estadual de Santa Cruz
Ilh?us/BA - Brasil
Fone: +55 73 3680-5622
E-mail:ivanalaman at gmail.com
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[[alternative HTML version deleted]]
> For years I have a problem that I have avoided with the use of the switch > function, but now I want to solve by following the good practices ofobject> orientation (OOP). > My function was created to generate experiments according to some input > parameters. Therefore, the first argument does not have a class defined as > "data.frame", "matrix", etc., so that from the generic, specific methodscan> be called. > I made a simple example to show my problem. > If anyone has any light I thank them immensely.Welcome to the world of OOP. Possibly my favorite topic. :) However, I don't understand your question.> foo(a = 1)This is not how method dispatch is designed to work. Lets say you have a function to create a brazil (Brazil) object. (Which sets or prepends "brazil" to the class attribute).> brazil = function (...some.arguments...) > { x = ...some.thing... > class (x) = c ("brazil", class (x) ) > ...some.other.constructor.code.... > ...return.x... > }Then you would write:> b = brazil () > foo (b, a=1) # not foo (a=1)And the brazil method would be called for generic foo and object b. Note that there are many variations of this approach. And someone will probably correct me, if I don't also mention that R has two main object oriented systems. This one relates to S3, the other is S4 partly implemented in the methods package. [[alternative HTML version deleted]]
Hello,
Your foo.default is wrong in:
1) The general principle. S3 methods dispatch on the class attribute,
you cannot expect to set that attribute in foo.default
and have it call/dispatch
and have it call/dispatch
and ...
2) Even if this were possible, your assignment of the class attribute is
wrong, you assign "foo.brazil" and "foo.argentina" so the
methods to be
called would be, respectively,
foo.foo.brazil
foo.foo.argentina
Nonsense! But in fact it's just a typo.
Try assigning just "brazil" or "argentina" and error 1)
above (not very
well explained, BTW) will still occur.
A possible solution is to have a different generic, bar(), with methods
bar.brazil and bar.argentina. Something like this:
foo <- function (x, ...) UseMethod ('foo')
foo.default <- function(x, a = 10, b = NULL, cc = 2, dd = 3,
type = c('brazil', 'argentina'), ...){
ty <- match.arg(type)
obj <- list(a = a, b = b, cc = cc, dd = dd)
class (obj) <- ty
res <- bar(x = obj, ...)
res
}
bar <- function (x, ...) UseMethod ('bar')
bar.brazil <- function(x, ...){
a <- x$a
cc <- x$cc
res <- a + cc
res
}
bar.argentina <- function(x, ...){
cc <- x$cc
dd <- x$dd
res <- sqrt(cc + dd)
res
}
foo(a = 1)
#[1] 3
foo(a = 1, type = 'argentina')
#[1] 2.236068
Hope this helps,
Rui Barradas
?s 00:34 de 29/05/19, Ivan Bezerra Allaman escreveu:> Good night dear!
> For years I have a problem that I have avoided with the use of the switch
> function, but now I want to solve by following the good practices of object
> orientation (OOP).
> My function was created to generate experiments according to some input
> parameters. Therefore, the first argument does not have a class defined as
> "data.frame", "matrix", etc., so that from the generic,
specific methods can
> be called.
> I made a simple example to show my problem.
>
> foo <- function (x, ...) UseMethod ('foo')
>
> foo.default <- function(x,
> a = 10,
> b = NULL,
> cc = 2,
> dd = 3,
> type = c ('brazil', 'argentina'),
> ...){
>
> ty <- match.arg(type)
>
> obj <- list(a = a,
> b = b,
> cc = cc,
> dd = dd)
> class (obj) <- paste ('foo',
> ty,
> sep = '.')
>
> res <- foo(x = obj, ...)
> }
>
> foo.brazil <- function(x, ...){
> a <- x$a
> cc <- x$cc
> res <- a + cc
> return (res)
> }
>
> foo.argentina <- function(x, ...){
> cc <- x$cc
> dd <- x$dd
> res <- sqrt(cc + dd)
> return (res)
> }
>
> foo(a = 1)
>
> If anyone has any light I thank them immensely.
>
Hello, Inline. ?s 10:06 de 31/05/19, Rui Barradas escreveu:> Hello, > > Your foo.default is wrong in: > > 1) The general principle. S3 methods dispatch on the class attribute, > you cannot expect to set that attribute in foo.default > > ?and have it call/dispatch > ?and have it call/dispatch > ?and ...Let me make this more clear. Your foo.default, with an extra code line right after assigning the class to obj, print(class(obj)), outputs the following. [1] "foo.brazil" [1] "foo.brazil" [1] "foo.brazil" [1] "foo.brazil" <--- etc ---> [1] "foo.brazil" [1] "foo.brazil" [1] "foo.brazil" [1] "foo.brazil" Error: C stack usage 7972260 is too close to the limit It will never reach the methods you need. But if you correct the typo and assign like it is below, it will work as expected. foo <- function (x, ...) UseMethod ('foo') foo.default <- function(x, a = 10, b = NULL, cc = 2, dd = 3, type = c ('brazil', 'argentina'), ...){ ty <- match.arg(type) obj <- list(a = a, b = b, cc = cc, dd = dd) class (obj) <- ty res <- foo(x = obj, ...) res } foo.brazil <- function(x, ...){ a <- x$a cc <- x$cc res <- a + cc res } foo.argentina <- function(x, ...){ cc <- x$cc dd <- x$dd res <- sqrt(cc + dd) res } foo(a = 1) #[1] 3 foo(a = 1, type = "argentina") #[1] 2.236068 Hope this helps, Rui Barradas> > 2) Even if this were possible, your assignment of the class attribute is > wrong, you assign "foo.brazil" and "foo.argentina" so the methods to be > called would be, respectively, > > foo.foo.brazil > foo.foo.argentina > > Nonsense! But in fact it's just a typo. > > Try assigning just "brazil" or "argentina" and error 1) above (not very > well explained, BTW) will still occur. > > > A possible solution is to have a different generic, bar(), with methods > bar.brazil and bar.argentina. Something like this: > > > foo <- function (x, ...) UseMethod ('foo') > > foo.default <- function(x, a = 10, b = NULL, cc = 2, dd = 3, > ??????????????????????? type = c('brazil', 'argentina'), ...){ > > ? ty <- match.arg(type) > > ? obj <- list(a = a, b = b, cc = cc, dd = dd) > ? class (obj) <- ty > ? res <- bar(x = obj, ...) > ? res > } > > bar <- function (x, ...) UseMethod ('bar') > bar.brazil <- function(x, ...){ > ? a <- x$a > ? cc <- x$cc > ? res <- a + cc > ? res > } > > bar.argentina <- function(x, ...){ > ? cc <- x$cc > ? dd <- x$dd > ? res <- sqrt(cc + dd) > ? res > } > > foo(a = 1) > #[1] 3 > > foo(a = 1, type = 'argentina') > #[1] 2.236068 > > > Hope this helps, > > Rui Barradas > > > ?s 00:34 de 29/05/19, Ivan Bezerra Allaman escreveu: >> Good night dear! >> For years I have a problem that I have avoided with the use of the switch >> function, but now I want to solve by following the good practices of >> object >> orientation (OOP). >> My function was created to generate experiments according to some input >> parameters. Therefore, the first argument does not have a class >> defined as >> "data.frame", "matrix", etc., so that from the generic, specific >> methods can >> be called. >> I made a simple example to show my problem. >> >> foo <- function (x, ...) UseMethod ('foo') >> >> foo.default <- function(x, >> ???????????????????????? a = 10, >> ???????????????????????? b = NULL, >> ???????????????????????? cc = 2, >> ???????????????????????? dd = 3, >> ???????????????????????? type = c ('brazil', 'argentina'), >> ???????????????????????? ...){ >> >> ?? ty <- match.arg(type) >> >> ?? obj <- list(a = a, >> ????????????????? b = b, >> ????????????????? cc = cc, >> ????????????????? dd = dd) >> ?? class (obj) <- paste ('foo', >> ??????????????????????????????????? ty, >> ?????????????????????????????????? sep = '.') >> >> ?? res <- foo(x = obj, ...) >> } >> >> foo.brazil <- function(x, ...){ >> ?? a <- x$a >> ?? cc <- x$cc >> ?? res <- a + cc >> ?? return (res) >> } >> >> foo.argentina <- function(x, ...){ >> ?? cc <- x$cc >> ?? dd <- x$dd >> ?? res <- sqrt(cc + dd) >> ?? return (res) >> } >> >> foo(a = 1) >> >> If anyone has any light I thank them immensely. >> > > ______________________________________________ > R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see > 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.