[R] [External] Re: [External] Adding a superscript 6 to a number

[David Winsemius]

On 12/29/20 3:45 PM, Jeff Newmiller wrote:
> This doesn't sound right. When you use expression() it freezes the syntax as the expression you wrote, so expression(paste(x^2,"[", m^2, "]")) is a perfectly valid plotmath expression. The expression() call is _not_ an "inverse" of paste because the presence of paste is supporting the inclusion of non-syntactic elements in this context... it is handled by plotmath, not by actually executing paste(), and expression is delaying evaluation to give plotmath a chance to combine the sub expressions including character literals without as.character or a subsequent eval().
>
> Code that invokes paste on an expression seems unwise to me... but not the other way around.

There are three instances of `expression(paste(...))` in the examples 
for plotmath, so Heiberger's perspective was not adopted by the S/R 
plotmath authors. It behaves a bit like `paste0` inside plotmath. In my 
opinion its use in plotmath expressions makes the code less readable 
than if one were to just use "*" as a concatenation operator. The 
example in ?plotmath :


main = expression(paste(plain(sin) * phi, "  and  ",
                                 plain(cos) * phi))

... could be better expressed as:

main = expression( plain(sin) * phi *  "  and  " * plain(cos) * phi )


The usual `paste` has a "sep" and "collapse" arguments. The plotmath 
`paste` function does not honor those arguments.


-- 

David.

>
> On December 29, 2020 3:05:21 PM PST, Bert Gunter <bgunter.4567 using gmail.com> wrote:
>> ... yes, more specifically:
>>
>> (from ?paste)
>> "paste converts its arguments (*via* as.character
>> <http://127.0.0.1:33923/help/library/base/help/as.character>) to
>> character
>> strings, and concatenates them (separating them by the string given by
>> sep).
>> "
>>
>> More to the point, I would say, is that if you need to manipulate
>> expressions or other language objects you should live in the world of
>> language objects, rather than converting them back and forth to
>> character
>> strings.  But this may be off topic and in the weeds;  for which, if
>> so,
>> apologies.
>>
>> Cheers,
>> Bert
>>
>>
>> Bert Gunter
>>
>> "The trouble with having an open mind is that people keep coming along
>> and
>> sticking things into it."
>> -- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )
>>
>>
>> On Tue, Dec 29, 2020 at 2:57 PM Richard M. Heiberger <rmh using temple.edu>
>> wrote:
>>
>>> It is a generalization.
>>> Don't use paste() and expression() together because paste is a
>> sort-of
>>> inverse to expression.
>>> In this example I start by typing several characters, and the result
>>> of paste(expression()) is a string containing the characters I
>>> initially typed.
>>>
>>>> expression(12^6)
>>> expression(12^6)
>>>> paste(expression(12^6))
>>> [1] "12^6"
>>>
>>>
>>> expression(12^6)
>>> paste(expression(12^6))
>>>
>>> plot(0:1, 0:1)
>>> text(.1, .4, labels=paste(expression(12^6)))
>>> text(.1, .3, labels=expression(12^6))
>>>
>>> On Tue, Dec 29, 2020 at 4:15 PM Jeff Newmiller
>> <jdnewmil using dcn.davis.ca.us>
>>> wrote:
>>>> Why not? Is that a generalization, or specific to this case?
>>>>
>>>> On December 29, 2020 7:54:22 AM PST, "Richard M. Heiberger" <
>>> rmh using temple.edu> wrote:
>>>>> paste() is the problem.  don’t use paste with expression()
>>>>>
>>>>> On Tue, Dec 29, 2020 at 10:50 Sorkin, John
>> <jsorkin using som.umaryland.edu>
>>>>> wrote:
>>>>>
>>>>>> Colleagues,
>>>>>>
>>>>>> I would like to create a number (stored in the variable x) to
>> the
>>>>> number
>>>>>> with the exponent of, i.e. the number to the sixth power. The
>> code I
>>>>> have
>>>>>> tried, pasted below does not work.
>>>>>>
>>>>>> # create plot
>>>>>> plot(x=0.2,y=0.2,xlim=c(0,1),ylim=c(0,1))
>>>>>> PNotSusp=0.69
>>>>>> # Create a string containing the base and exponent.
>>>>>> x <- 0.95123
>>>>>> # Convert the base to text and add the exponent of 6
>>>>>> mylab <- expression(paste(" ",character(x)^6))
>>>>>> # Add the text to the plot
>>>>>> text(0.4,0.8,labels=paste(PNotSusp,"=\n",mylab))
>>>>>>
>>>>>> I hope someone can show me how to create the text string I need.
>>>>>>
>>>>>> Thank you,
>>>>>> John
>>>>>>
>>>>>> John David Sorkin M.D., Ph.D.
>>>>>> Professor of Medicine
>>>>>> Chief, Biostatistics and Informatics
>>>>>> University of Maryland School of Medicine Division of
>> Gerontology and
>>>>>> Geriatric Medicine
>>>>>> Baltimore VA Medical Center
>>>>>> 10 North Greene Street
>>>>>>
>>>>> <
>> https://www.google.com/maps/search/10+North+Greene+Street?entry=gmail&source=g
>>>>>> GRECC (BT/18/GR)
>>>>>> Baltimore, MD 21201-1524
>>>>>> (Phone) 410-605-7119
>>>>>> (Fax) 410-605-7913 (Please call phone number above prior to
>> faxing)
>>>>>>
>>>>>> ______________________________________________
>>>>>> R-help using r-project.org mailing list -- To UNSUBSCRIBE and more,
>> see
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>>>>>> PLEASE do read the posting guide
>>>>>> http://www.R-project.org/posting-guide.html
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>> code.
>>>>>        [[alternative HTML version deleted]]
>>>>>
>>>>> ______________________________________________
>>>>> R-help using 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.
>>>> --
>>>> Sent from my phone. Please excuse my brevity.
>>> ______________________________________________
>>> R-help using 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.
>>>