[R] italics letter in roman string

[Chabot Denis]

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
>
>