[R] italics letter in roman string

[Gabor Grothendieck]

Its a formula, not an expression -- but it will coerce formulas.  Without ~
its no longer a formula.

On 3/18/07, Chabot Denis <chabotd at globetrotter.net> wrote:
> Wow, this works, Gabor, but I am mystified. I would have tought an
> expression needed the word expression, and/or a text string needed to
> be within quotes. What is happening here, exactly? Why the use of
> "~"? I tried without and it no longer works.
>
> Thanks in advance,
>
> Denis
> Le 07-03-18 à 08:59, Gabor Grothendieck a écrit :
>
> > Sorry, legend= was omitted:
> >
> > plot(1:10)
> > legend("topleft", legend = This ~ study ~ italic(n) == 3293)
> >
> > On 3/18/07, Chabot Denis <chabotd at globetrotter.net> wrote:
> >> Thank you Marc, Jim and Gabor,
> >>
> >> I like the solution with "expression", nice and simple. Gabor, your
> >> solution did not work, probably just a matter of putting the text
> >> inside an expression?
> >>
> >> However it would be nice if the help system pointed to it. A search
> >> on "italics" brought me nothing, one on "italic" gave me 4 hits, none
> >> useful. And reading the help on plotmath, I found no mention of
> >> italic
> >> (). Where can we suggest additions to the help system?
> >>
> >> I must plead guilty to have forgotten a RSiteSearch before posting. I
> >> just did and I think I might have figured out something out there.
> >> But your answers were nice and to the point!
> >>
> >> Cheers,
> >>
> >> Denis
> >> Le 07-03-17 à 23:30, Marc Schwartz a écrit :
> >>
> >> > On Sat, 2007-03-17 at 21:56 -0500, Marc Schwartz wrote:
> >> >> On Sat, 2007-03-17 at 22:01 -0400, Chabot Denis wrote:
> >> >>> Hi,
> >> >>>
> >> >>> As part of the legend to a plot, I need to have the "n" in
> >> italics
> >> >>> because it is a requirement of the journal I aim to publish in:
> >> >>> "This study, n = 3293"
> >> >>>
> >> >>> Presently I have:
> >> >>> legend(20, 105, "This study, n = 3293", pch=1,  col=rgb
> >> (0,0,0,0.5),
> >> >>>                  pt.cex=0.3, cex=0.8, bty="n")
> >> >>>
> >> >>> I suppose I could leave a blank in place of the "n", then issue a
> >> >>> text call where I'd use font=3 for a single letter, "n". But
> >> it will
> >> >>> be tricky to find the exact location to use.
> >> >>>
> >> >>> Is there a way to switch to font=3 just for one letter within a
> >> >>> string?
> >> >>>
> >> >>> Thanks in advance,
> >> >>>
> >> >>> Denis Chabot
> >> >>
> >> >> Denis,
> >> >>
> >> >> Try something like this:
> >> >>
> >> >> plot(20, 100)
> >> >>
> >> >> leg <- legend(20, 105, "This study,    = 3293", pch = 1,
> >> >>               col=rgb(0,0,0,0.5), pt.cex = 0.3, cex = 0.8,
> >> >>               bty = "n")
> >> >>
> >> >> text(leg$text$x + strwidth("This study, ", cex = 0.8),
> >> >>      leg$text$y, "n", font = 3, cex = 0.8, adj = c(0, 0.5))
> >> >>
> >> >>
> >> >> Note that legend returns a list structure, which contains the x
> >> and y
> >> >> coordinates of the start of the text strings that are plotted. So
> >> >> I get
> >> >> that information for your line of text.
> >> >>
> >> >> Next, I use strwidth() to calculate, in user coordinates, the
> >> >> length of
> >> >> the characters preceding the 'n', including spaces.  We add that
> >> >> distance to the x coordinate returned in the legend call.
> >> >>
> >> >> I also use the 'adj' argument in the text() call, so that it is in
> >> >> synch
> >> >> with the same parameters in legend() for alignment with the other
> >> >> letters.
> >> >>
> >> >> See ?strwidth for more information.
> >> >>
> >> >> You may have to tweak the horizontal spacing of the 'n' a bit,
> >> >> depending
> >> >> upon the rest of your graph.
> >> >
> >> > Denis,
> >> >
> >> > I thought of another approach, using plotmath.
> >> >
> >> > First, create a text expression, specifying that the 'n' should be
> >> > italicized. Then use that expression in the legend() call.
> >> >
> >> > txt <- expression(paste("This study, ", italic(n), " = 3293"))
> >> >
> >> > plot(20, 100)
> >> >
> >> > legend(20, 105, txt, pch = 1, col=rgb(0,0,0,0.5),
> >> >        pt.cex = 0.3, cex = 0.8, bty = "n")
> >> >
> >> >
> >> > That's easier that the first solution.  See ?plotmath
> >> >
> >> > HTH,
> >> >
> >> > Marc Schwartz
> >> >
> >> >
> >>
> >>
>
>