R devel - Oct 1999 - Wrong text() adjustment with (math)expression and "\n" (PR#299)

This is adapted from  partha_bagchi@hgsi.com 's report on R-help:

     plot(0); title(expression("Bad\n with much much more text")))

gives something like 

      Bad
          with much much more text

(``newline w/o carriage return'') instead of centering both lines such
as

               Bad
     with much much more text

which is produced by (just dropping `expression' from the above)

      plot(0); title(("Bad\n with much much more text"))

By the way, the following would need even more attention if one insists on 
correct behavior:

plot(0)
title(expression(paste("Still works with math\n", "with", 
                       frac(1,sum(x[i], i==1,n)), " and more text")))

Martin Maechler <maechler@stat.math.ethz.ch>
http://stat.ethz.ch/~maechler/

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maechler@stat.math.ethz.ch writes:
> This is adapted from  partha_bagchi@hgsi.com 's report on R-help:
> 
>      plot(0); title(expression("Bad\n with much much more
text")))
> 
> gives something like 
> 
>       Bad
>           with much much more text
> 
> (``newline w/o carriage return'') instead of centering both lines
such as
> 
>                Bad
>      with much much more text
> 
> which is produced by (just dropping `expression' from the above)
> 
>       plot(0); title(("Bad\n with much much more text"))
> 
> By the way, the following would need even more attention if one insists on 
> correct behavior:
> 
> plot(0)
> title(expression(paste("Still works with math\n",
"with",
>                        frac(1,sum(x[i], i==1,n)), " and more
text")))
I'm not sure I'm buying that this is a bug. To see what is really
going on try something like:

 plot(0);title(expression(mu*"a\nbc"*eta*"ab\nc"*xi))

what happens is that the strings get set *individually* as multiline
text with (left,bottom) adjustment. If you look closer, Martin's
example really gives

      Bad
      with much much more text

We could relatively easily make the adjustment (center,center) I think,
but that isn't very useful, and Partha was expecting the whole thing to
continue on a new line. I think that is rather difficult to achieve
because the relation between the expression as text and as a parse
tree is not linear and things mean different things in different
positions (consider "a\nb"+"a\nb"^"a\nb"). To
actually have a formula
title split over several lines, I'd suggest fiddling with mtext().


-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard@biostat.ku.dk)             FAX: (+45) 35327907
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