Ruby Gnuplot and Backslash

I recently stumbled upon a distracting issue when trying to get the gnuplot gem to output LaTeX-syntax.

Ideally I would like:

plot.ylabel "$\\mu$"
plot.xlabel "$\\epsilon$"

to produce something like:

\put(160,2853){\rotatebox{-270}{\makebox(0,0){\strut{}$\mu$}}}%
\put(3023,140){\makebox(0,0){\strut{}$\epsilon$}}%

but it produces:

\put(160,2853){\rotatebox{-270}{\makebox(0,0){\strut{}$mu$}}}%
\put(3023,140){\makebox(0,0){\strut{}$epsilon$}}%

Notice how the \ is omitted? Thats frustrating when you try to automate things…

The solution is to escape the backslashes some more:

plot.ylabel "$\\\\mu$"
plot.xlabel "$\\\\epsilon$"

which produces the desired result.

Consulting the source one can find out why. Anyhow, I think I know my “client”, and the default x/y-label placement will not cut it – hence the following (the dataset is just mumbojumbo):

require "gnuplot"

filename = "2015_1"

Gnuplot.open do |gp|
  Gnuplot::Plot.new( gp ) do |plot|

    plot.terminal "epslatex size 10cm,10cm standalone 10 monochrome dashed "

    plot.output "./#{filename}.tex"

    plot.lmargin 6
    plot.bmargin 4
    plot.unset 'border'
    plot.unset 'tics'
    plot.unset 'key'

    x_min = 1
    x_max = 500
    y_min = 0
    y_max = 70

    plot.set "style arrow 1 head filled size screen 0.02,15,10 ls 1"

    #explicit arrow on x-axis
    plot.set "arrow from #{x_min} to #{x_max+10} as 1"
    #explicit arrow on y-axis
    plot.set "arrow from #{x_min},#{y_min} to #{x_min},#{y_max+2} as 1"


    plot.xrange "[#{x_min}:#{x_max}]"
    plot.yrange "[#{y_min}:#{y_max}]"

    plot.title  "Lorem ipsum"

    # x-label
    plot.label "'$\\varepsilon$' at #{x_max-20}, -5"
    # y-label
    plot.label "'$\\mu$' at -25, #{y_max-5}"

    plot.data << Gnuplot::DataSet.new( "45*sin((x/8)**2)" ) do |ds|
      ds.with = "lines"
      ds.linewidth = 1
    end

  end
end
puts "created #{filename}.tex"

%x(rubber #{filename}.tex)
%x(dvips #{filename}.dvi -o #{filename}.ps)
%x(ps2eps #{filename}.ps -f)
%x(dvipdf #{filename}.dvi #{filename}.pdf)
%x(dvipng #{filename}.dvi -o #{filename}.png)
%x(gs -dNOPAUSE -q -dBATCH -sDEVICE=tiff24nc -r300 -sOutputFile=#{filename}.tiff #{filename}.ps)