[R] plotmath and logical operators?

[Bert Gunter]

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 <macqueen1 using 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.4567 using gmail.com>
> *Date: *Monday, August 20, 2018 at 3:38 PM
> *To: *"MacQueen, Don" <macqueen1 using llnl.gov>
> *Cc: *array R-help <r-help using 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 using 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
>
>
>
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