As I understand it, the problem is: "A mathematical expression must obey the normal rules of syntax for any *R* expression, but it is interpreted according to very different rules than for normal *R* expressions."
I believe this means that you cannot do what you wanted to using plotmath. Cheers, Bert On Mon, Aug 20, 2018 at 4:14 PM MacQueen, Don <macque...@llnl.gov> wrote: > Thanks Bert! > > > > It certainly works for the example (and shows a much deeper understanding > of eval, substitute, etc. than I have). But it doesn't appear to generalize > very well in the way I need (which of course I didn't think of mentioning > until after I sent the email -- sorry). > > > > Suppose subs is any expression that would be valid for the subset argument > of base::subset, for a given data frame. Then I can extract that subset of > the data frame by using > > mydf[ with(mydf, eval(subs)) , ] > > (or similar). > > > > Then, having plotted some aspect of that subset, I want to annotate the > plot with the subset specifications. > > > > I've used this approach to set up a system that helps me to interactively > review various subsets of a large set of data. I save the final selected > subsetting expressions in some sort of data structure, for later use in > preparing a report using rmarkdown. > > > > I was hoping to use plotmath to improve the appearance of the annotations > -- but I now think it's not worth this kind of effort. I think I'm going to > settle for mtext( as.character(subs) ). > > > > -Don > > > > -- > > Don MacQueen > > Lawrence Livermore National Laboratory > > 7000 East Ave., L-627 > > Livermore, CA 94550 > > 925-423-1062 > > Lab cell 925-724-7509 > > > > > > > > *From: *Bert Gunter <bgunter.4...@gmail.com> > *Date: *Monday, August 20, 2018 at 3:38 PM > *To: *"MacQueen, Don" <macque...@llnl.gov> > *Cc: *array R-help <r-help@r-project.org> > *Subject: *Re: [R] plotmath and logical operators? > > > > This is clumsy and probably subject to considerable improvement, but does > it work for you: > > > > left <- quote(x >= 3) > right <- quote(y <= 3) ## these can be anything > > > > ## the plot: > > plot(1) > > eval(substitute(mtext(expression(paste(left, " & ",right))), list(left = > left, right = right))) > > > > ## Expression evaluation > > eval(substitute(with(df,left & right), list(left = left, right = right))) > > 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 Mon, Aug 20, 2018 at 2:00 PM MacQueen, Don via R-help < > r-help@r-project.org> wrote: > > I would like to use plotmath to annotate a plot with an expression that > includes a logical operator. > > ## works well > tmp <- expression(x >= 3) > plot(1) > mtext(tmp) > > ## not so well > tmp <- expression(x >= 3 & y <= 3) > plot(1) > mtext(tmp) > > Although the text that's displayed makes sense, it won't be obvious to my > non-mathematical audience. > > I'd appreciate suggestions. > > > I've found a work-around that gets the annotation to look right > tmpw <- expression(paste( x >= 3, " & ", y <= 3) ) > plot(1) > mtext(tmpw) > > > But it breaks my original purpose, illustrated by this example: > > df <- data.frame(x=1:5, y=1:5) > tmp <- expression(x >= 3 & y <= 3) > tmpw <- expression(paste( x >= 3, " & ", y <= 3) ) > with(df, eval(tmp)) > [1] FALSE FALSE TRUE FALSE FALSE > with(df, eval(tmpw)) > [1] "FALSE & TRUE" "FALSE & TRUE" "TRUE & TRUE" "TRUE & FALSE" > "TRUE & FALSE" > > Thanks > -Don > > -- > Don MacQueen > Lawrence Livermore National Laboratory > 7000 East Ave., L-627 > Livermore, CA 94550 > 925-423-1062 > Lab cell 925-724-7509 > > > > ______________________________________________ > 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.
