subject:"\[R\] formula argument evaluation"

Re: [R] formula argument evaluation

2016-04-14 Thread Adrian Dușa

Thanks Bill, it's very useful to know how parsing and evaluation works.
It seems that quoting is the least complicated solution which is guaranteed
to work.

Best,
Adrian
On 13 Apr 2016 6:04 p.m., "William Dunlap"  wrote:

> %=>% would have precendence ('order of operations') problems also.
>
>A + B %=>% C
>
> is equivalent to
>
>   A + ( B %=>% C)
>
> and I don't think that is what you want.
>
> as.list(quote(A + B %=>% C)) shows the first branch in the parse tree.
> The following function, str.language, shows the entire parse tree, as in
>
>   > str.language(quote(A + B %=>% C))
>   `quote(A + B %=>% C)` call(3): A + B %=>% C
> `` name(1): +
> `` name(1): A
> `` call(3): B %=>% C
>   `` name(1): %=>%
>   `` name(1): B
>   `` name(1): C
>
> str.language <-
> function (object, ..., level = 0, name = myDeparse(substitute(object)))
> {
> abbr <- function(string, maxlen = 25) {
> if (length(string) > 1 || nchar(string) > maxlen)
> paste(substring(string[1], 1, maxlen), "...", sep = "")
> else string
> }
> myDeparse <- function(object) {
> if (!is.environment(object)) {
> deparse(object)
> }
> else {
> ename <- environmentName(object)
> if (ename == "")
> ename <- ""
> paste(sep = "", "<", ename, "> ", paste(collapse = " ",
> objects(object)))
> }
> }
> cat(rep("  ", level), sep = "")
> if (is.null(name))
> name <- ""
> cat(sprintf("`%s` %s(%d): %s\n", abbr(name), class(object),
> length(object), abbr(myDeparse(object
> a <- attributes(object)
> if (is.recursive(object) && !is.environment(object)) {
> object <- as.list(object)
> names <- names(object)
> for (i in seq_along(object)) {
> str.language(object[[i]], ..., level = level + 1,
> name = names[i])
> }
> }
> a$names <- NULL
> if (length(a) > 0) {
> str.language(a, level = level + 1, name = paste("Attributes of",
> abbr(name)))
> }
> }
>
>
>
> Bill Dunlap
> TIBCO Software
> wdunlap tibco.com
>
> On Tue, Apr 12, 2016 at 11:59 PM, Adrian Dușa 
> wrote:
>
>> I suppose it would work, although "=>" is rather a descriptive symbol and
>> less a function.
>> But choosing between quoting:
>> "A + B => C"
>> and a regular function:
>> A + B %=>% C
>> probably quoting is the most straightforward, as the result of the foo()
>> function has to be a string anyways (which is parsed by other functions).
>>
>> On Tue, Apr 12, 2016 at 6:20 PM, Richard M. Heiberger 
>> wrote:
>>
>> > Would making it regular function %=>%, using "%" instead of quotes,
>> > work for you?
>> >
>> > On Tue, Apr 12, 2016 at 11:09 AM, Adrian Dușa 
>> > wrote:
>> > > On Tue, Apr 12, 2016 at 2:08 PM, Duncan Murdoch <
>> > murdoch.dun...@gmail.com>
>> > > wrote:
>> > >> [...]
>> > >>
>> > >> It never gets to evaluating it.  It is not a legal R statement, so
>> the
>> > > parser signals an error.
>> > >> If you want to pass arbitrary strings to a function, you need to put
>> > them
>> > > in quotes.
>> > >
>> > > I see. I thought it was parsed inside the function, but if it's parsed
>> > > before then quoting is the only option.
>> > >
>> > >
>> > > To Keith: no, I mean it like this "A + B => C" which is translated as:
>> > > "the union of A and B is sufficient for C" in set theoretic language.
>> > >
>> > > The "=>" operator means sufficiency, while "<=" means necessity.
>> Quoting
>> > > the expression is good enough, I was just curious if the quotes could
>> be
>> > > made redundant, somehow.
>> > >
>> > > Thank you both,
>> > > Adrian
>> > >
>> > > --
>> > > Adrian Dusa
>> > > University of Bucharest
>> > > Romanian Social Data Archive
>> > > Soseaua Panduri nr.90
>> > > 050663 Bucharest sector 5
>> > > Romania
>> > >
>> > > [[alternative HTML version deleted]]
>> > >
>> > > __
>> > > R-help@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.
>> >
>>
>>
>>
>> --
>> Adrian Dusa
>> University of Bucharest
>> Romanian Social Data Archive
>> Soseaua Panduri nr.90
>> 050663 Bucharest sector 5
>> Romania
>>
>> [[alternative HTML version deleted]]
>>
>> __
>> R-help@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.
>
>
>

[[alternative HTML version deleted]]

Re: [R] formula argument evaluation

2016-04-13 Thread William Dunlap via R-help

%=>% would have precendence ('order of operations') problems also.

   A + B %=>% C

is equivalent to

  A + ( B %=>% C)

and I don't think that is what you want.

as.list(quote(A + B %=>% C)) shows the first branch in the parse tree.  The
following function, str.language, shows the entire parse tree, as in

  > str.language(quote(A + B %=>% C))
  `quote(A + B %=>% C)` call(3): A + B %=>% C
`` name(1): +
`` name(1): A
`` call(3): B %=>% C
  `` name(1): %=>%
  `` name(1): B
  `` name(1): C

str.language <-
function (object, ..., level = 0, name = myDeparse(substitute(object)))
{
abbr <- function(string, maxlen = 25) {
if (length(string) > 1 || nchar(string) > maxlen)
paste(substring(string[1], 1, maxlen), "...", sep = "")
else string
}
myDeparse <- function(object) {
if (!is.environment(object)) {
deparse(object)
}
else {
ename <- environmentName(object)
if (ename == "")
ename <- ""
paste(sep = "", "<", ename, "> ", paste(collapse = " ",
objects(object)))
}
}
cat(rep("  ", level), sep = "")
if (is.null(name))
name <- ""
cat(sprintf("`%s` %s(%d): %s\n", abbr(name), class(object),
length(object), abbr(myDeparse(object
a <- attributes(object)
if (is.recursive(object) && !is.environment(object)) {
object <- as.list(object)
names <- names(object)
for (i in seq_along(object)) {
str.language(object[[i]], ..., level = level + 1,
name = names[i])
}
}
a$names <- NULL
if (length(a) > 0) {
str.language(a, level = level + 1, name = paste("Attributes of",
abbr(name)))
}
}



Bill Dunlap
TIBCO Software
wdunlap tibco.com

On Tue, Apr 12, 2016 at 11:59 PM, Adrian Dușa  wrote:

> I suppose it would work, although "=>" is rather a descriptive symbol and
> less a function.
> But choosing between quoting:
> "A + B => C"
> and a regular function:
> A + B %=>% C
> probably quoting is the most straightforward, as the result of the foo()
> function has to be a string anyways (which is parsed by other functions).
>
> On Tue, Apr 12, 2016 at 6:20 PM, Richard M. Heiberger 
> wrote:
>
> > Would making it regular function %=>%, using "%" instead of quotes,
> > work for you?
> >
> > On Tue, Apr 12, 2016 at 11:09 AM, Adrian Dușa 
> > wrote:
> > > On Tue, Apr 12, 2016 at 2:08 PM, Duncan Murdoch <
> > murdoch.dun...@gmail.com>
> > > wrote:
> > >> [...]
> > >>
> > >> It never gets to evaluating it.  It is not a legal R statement, so the
> > > parser signals an error.
> > >> If you want to pass arbitrary strings to a function, you need to put
> > them
> > > in quotes.
> > >
> > > I see. I thought it was parsed inside the function, but if it's parsed
> > > before then quoting is the only option.
> > >
> > >
> > > To Keith: no, I mean it like this "A + B => C" which is translated as:
> > > "the union of A and B is sufficient for C" in set theoretic language.
> > >
> > > The "=>" operator means sufficiency, while "<=" means necessity.
> Quoting
> > > the expression is good enough, I was just curious if the quotes could
> be
> > > made redundant, somehow.
> > >
> > > Thank you both,
> > > Adrian
> > >
> > > --
> > > Adrian Dusa
> > > University of Bucharest
> > > Romanian Social Data Archive
> > > Soseaua Panduri nr.90
> > > 050663 Bucharest sector 5
> > > Romania
> > >
> > > [[alternative HTML version deleted]]
> > >
> > > __
> > > R-help@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.
> >
>
>
>
> --
> Adrian Dusa
> University of Bucharest
> Romanian Social Data Archive
> Soseaua Panduri nr.90
> 050663 Bucharest sector 5
> Romania
>
> [[alternative HTML version deleted]]
>
> __
> R-help@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.

[[alternative HTML version deleted]]

__
R-help@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.

Re: [R] formula argument evaluation

2016-04-13 Thread Adrian Dușa

I suppose it would work, although "=>" is rather a descriptive symbol and
less a function.
But choosing between quoting:
"A + B => C"
and a regular function:
A + B %=>% C
probably quoting is the most straightforward, as the result of the foo()
function has to be a string anyways (which is parsed by other functions).

On Tue, Apr 12, 2016 at 6:20 PM, Richard M. Heiberger 
wrote:

> Would making it regular function %=>%, using "%" instead of quotes,
> work for you?
>
> On Tue, Apr 12, 2016 at 11:09 AM, Adrian Dușa 
> wrote:
> > On Tue, Apr 12, 2016 at 2:08 PM, Duncan Murdoch <
> murdoch.dun...@gmail.com>
> > wrote:
> >> [...]
> >>
> >> It never gets to evaluating it.  It is not a legal R statement, so the
> > parser signals an error.
> >> If you want to pass arbitrary strings to a function, you need to put
> them
> > in quotes.
> >
> > I see. I thought it was parsed inside the function, but if it's parsed
> > before then quoting is the only option.
> >
> >
> > To Keith: no, I mean it like this "A + B => C" which is translated as:
> > "the union of A and B is sufficient for C" in set theoretic language.
> >
> > The "=>" operator means sufficiency, while "<=" means necessity. Quoting
> > the expression is good enough, I was just curious if the quotes could be
> > made redundant, somehow.
> >
> > Thank you both,
> > Adrian
> >
> > --
> > Adrian Dusa
> > University of Bucharest
> > Romanian Social Data Archive
> > Soseaua Panduri nr.90
> > 050663 Bucharest sector 5
> > Romania
> >
> > [[alternative HTML version deleted]]
> >
> > __
> > R-help@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.
>



-- 
Adrian Dusa
University of Bucharest
Romanian Social Data Archive
Soseaua Panduri nr.90
050663 Bucharest sector 5
Romania

[[alternative HTML version deleted]]

__
R-help@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.

Re: [R] formula argument evaluation

2016-04-12 Thread Richard M. Heiberger

Would making it regular function %=>%, using "%" instead of quotes,
work for you?

On Tue, Apr 12, 2016 at 11:09 AM, Adrian Dușa  wrote:
> On Tue, Apr 12, 2016 at 2:08 PM, Duncan Murdoch 
> wrote:
>> [...]
>>
>> It never gets to evaluating it.  It is not a legal R statement, so the
> parser signals an error.
>> If you want to pass arbitrary strings to a function, you need to put them
> in quotes.
>
> I see. I thought it was parsed inside the function, but if it's parsed
> before then quoting is the only option.
>
>
> To Keith: no, I mean it like this "A + B => C" which is translated as:
> "the union of A and B is sufficient for C" in set theoretic language.
>
> The "=>" operator means sufficiency, while "<=" means necessity. Quoting
> the expression is good enough, I was just curious if the quotes could be
> made redundant, somehow.
>
> Thank you both,
> Adrian
>
> --
> Adrian Dusa
> University of Bucharest
> Romanian Social Data Archive
> Soseaua Panduri nr.90
> 050663 Bucharest sector 5
> Romania
>
> [[alternative HTML version deleted]]
>
> __
> R-help@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.

__
R-help@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.

Re: [R] formula argument evaluation

2016-04-12 Thread Adrian Dușa

On Tue, Apr 12, 2016 at 2:08 PM, Duncan Murdoch 
wrote:
> [...]
>
> It never gets to evaluating it.  It is not a legal R statement, so the
parser signals an error.
> If you want to pass arbitrary strings to a function, you need to put them
in quotes.

I see. I thought it was parsed inside the function, but if it's parsed
before then quoting is the only option.

To Keith: no, I mean it like this "A + B => C" which is translated as:
"the union of A and B is sufficient for C" in set theoretic language.

The "=>" operator means sufficiency, while "<=" means necessity. Quoting
the expression is good enough, I was just curious if the quotes could be
made redundant, somehow.

Thank you both,
Adrian

--
Adrian Dusa
University of Bucharest
Romanian Social Data Archive
Soseaua Panduri nr.90
050663 Bucharest sector 5
Romania

[[alternative HTML version deleted]]

__
R-help@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.

Re: [R] formula argument evaluation

2016-04-12 Thread Keith Jewell


On 12/04/2016 11:24, Adrian Dușa wrote:

I have a simple function such as:

foo <- function(x) {
 call <- lapply(match.call(), deparse)
 testit <- capture.output(tryCatch(eval(x), error = function(e) e))
 if (grepl("Error", testit)) {
 return(call$x)
 }
}

and I would like to detect a formula when x is not an object:

# this works

foo(A + B)

[1] "A + B"

# but this doesn't

foo(A + B => C)

Error: unexpected '=' in "foo(A + B ="

Can I prevent it from evaluating the "=" sign?
The addition sign "+" hasn't been evaluated, and I was hoping the "=" would
not get evaluated either. The "=>" sign is important for other purposes,
not related to this example.

Thank you in advance,
Adrian

--
Adrian Dusa
University of Bucharest
Romanian Social Data Archive
Soseaua Panduri nr.90
050663 Bucharest sector 5
Romania

[[alternative HTML version deleted]]


Did you mean
> foo (A + B >= C)
??

__
R-help@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.

Re: [R] formula argument evaluation

2016-04-12 Thread Duncan Murdoch


On 12/04/2016 6:24 AM, Adrian Dușa wrote:

I have a simple function such as:

foo <- function(x) {
 call <- lapply(match.call(), deparse)
 testit <- capture.output(tryCatch(eval(x), error = function(e) e))
 if (grepl("Error", testit)) {
 return(call$x)
 }
}

and I would like to detect a formula when x is not an object:

# this works

foo(A + B)

[1] "A + B"

# but this doesn't

foo(A + B => C)

Error: unexpected '=' in "foo(A + B ="

Can I prevent it from evaluating the "=" sign?


It never gets to evaluating it.  It is not a legal R statement, so the 
parser signals an error.


If you want to pass arbitrary strings to a function, you need to put 
them in quotes.


Duncan Murdoch


The addition sign "+" hasn't been evaluated, and I was hoping the "=" would
not get evaluated either. The "=>" sign is important for other purposes,
not related to this example.

Thank you in advance,
Adrian

--
Adrian Dusa
University of Bucharest
Romanian Social Data Archive
Soseaua Panduri nr.90
050663 Bucharest sector 5
Romania

[[alternative HTML version deleted]]

__
R-help@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.



__
R-help@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.

[R] formula argument evaluation

2016-04-12 Thread Adrian Dușa

I have a simple function such as:

foo <- function(x) {
call <- lapply(match.call(), deparse)
testit <- capture.output(tryCatch(eval(x), error = function(e) e))
if (grepl("Error", testit)) {
return(call$x)
}
}

and I would like to detect a formula when x is not an object:

# this works
> foo(A + B)
[1] "A + B"

# but this doesn't
> foo(A + B => C)
Error: unexpected '=' in "foo(A + B ="

Can I prevent it from evaluating the "=" sign?
The addition sign "+" hasn't been evaluated, and I was hoping the "=" would
not get evaluated either. The "=>" sign is important for other purposes,
not related to this example.

Thank you in advance,
Adrian

--
Adrian Dusa
University of Bucharest
Romanian Social Data Archive
Soseaua Panduri nr.90
050663 Bucharest sector 5
Romania

[[alternative HTML version deleted]]

__
R-help@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.

Re: [R] formula argument evaluation

Re: [R] formula argument evaluation

Re: [R] formula argument evaluation

Re: [R] formula argument evaluation

Re: [R] formula argument evaluation

Re: [R] formula argument evaluation

Re: [R] formula argument evaluation

[R] formula argument evaluation

8 matches

Site Navigation

Mail list logo

Footer information