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. On December 29, 2020 3:05:21 PM PST, Bert Gunter <bgunter.4...@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 <r...@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 ><jdnew...@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" < >> r...@temple.edu> wrote: >> > >paste() is the problem. don’t use paste with expression() >> > > >> > >On Tue, Dec 29, 2020 at 10:50 Sorkin, John ><jsor...@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@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. >> > >> > -- >> > Sent from my phone. Please excuse my brevity. >> >> ______________________________________________ >> 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. >> -- Sent from my phone. Please excuse my brevity. ______________________________________________ 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.
