\begin{lstlisting}[language=Gnuplot, basicstyle=\small\ttfamily, frame=single,
  float=htb, caption={Data fitting in gnuplot --- with the non-linear
formula}, label={lst:nlfit}]
gnuplot> f(x)=R0 + B*x + C*sin(G*x)
gnuplot> fit f(x) "measR.dat" via R0, B, C, G
R0              = 134.247          +/- 6.717        (5.003%)
B               = 18.5092          +/- 1.307        (7.063%)
C               = 15.0483          +/- 5.097        (33.87%)
G               = 0.663579         +/- 0.05086      (7.665%)
\end{lstlisting}