[R] plotmath "overstrikes" in output on a Linux system

Peter Dalgaard p.dalgaard at biostat.ku.dk
Tue Apr 8 11:09:21 CEST 2008

Paul Johnson wrote:
> I've been testing plotmath.  But I'm getting some funny output one one
> computer. The problem is that characters are 'jumbled' and overstrike
> when symbols are introduced.
> Sample code:
> mu <- 440.0
> sigma <- 12.5
> myx <- seq( mu - 4*sigma,  mu+ 4*sigma, length.out=500)
> myDensity <- dnorm(myx,mean=mu,sd=sigma)
> # Here's one way to retrieve the values of mu and sigma and insert
> them into an expression
> t1t2 <- bquote (paste("Normal(", mu== .(mu), ',', sigma== .(sigma),")") )
> plot(myx, myDensity, type="l", xlab="X", ylab="Probability Density ", main=t1t2)
> I have tested this code and it works on two desktop Fedora Linux 8
> systems to make a nice figure, but on a Dell Laptop with Fedora Linux
> 8 and R 2.6.2, something funny happens: the characters "overstrike"
> each other.  The Greek letter "mu" is printed several spaces to the
> left of the "(" that it is supposed to follow.  I made an itty  bitty
> picture of the figure title to show you:
> http://pj.freefaculty.org/R/plotmath_problem.png
> I can force in spaces to re-arrange the symbols so they do not
> overstrike. The following looks fine in the output.
> t1t2 <- bquote (paste("Normal (   ", mu== .(mu), '  ,  ', sigma==
> .(sigma)," )") )
> ### Note spaces manually inserted above are needed, otherwise plotmath
> overlaps "l" of
> plot(myx, myDensity, type="l", xlab="X", ylab="Probability Density ", main=t1t2)
> What do you suppose is wrong? The X configuration
My guess would be that something is wrong with the font metrics on one 
system. If the length of "Normal(" is miscalculated, that would explain 
the rest.

Do you see the same thing if you do something like

plot(0, main=quote(paste("Lengthy string", "A")))

It could be related to dpi settings; I seem to recall that this can do 
weird things on wide-screen displays. Doex xdpyinfo provide any clues? 
Look for lines like this

screen #0:
  dimensions:    1024x768 pixels (260x195 millimeters)
  resolution:    100x100 dots per inch
You could also play with the pointsize argument to X11() and see if the 
problem disappears at different sizes.

   O__  ---- Peter Dalgaard             Øster Farimagsgade 5, Entr.B
  c/ /'_ --- Dept. of Biostatistics     PO Box 2099, 1014 Cph. K
 (*) \(*) -- University of Copenhagen   Denmark      Ph:  (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)              FAX: (+45) 35327907

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