controllo della dimensione dei plot prodotti con gnuplottex

Vorrei controllare le dimensioni del plot mediante due variabili di lunghezza \w e \h. Ho provato così:

`
\newlength{\w}
\newlength{\h}
\setlength{\w}{15cm}
\setlength{\h}{10cm}
\begin{gnuplot}[terminal=lua, terminaloptions = size {\w,\h}]
set size 1,1
set border lt 1 lc rgb 'gray' lw 0.5
f(x)=log(1+exp(1)*x**2)
Xa = -2.5
Xb = 2.5
Ya = -0.3
Yb = 3
unset zeroaxis
unset xlabel
unset ylabel
set samples 200
set grid lt 3 lc rgb “gray” lw 0.5
set grid y2tics
set arrow 1 from Xa,0 to Xb,0,3 head back filled lt rgb “blue” linewidth 1.000 size screen 0.018,14.000,45.000
set arrow 2 from 0,Ya to 0,Yb,3 head back filled lt rgb “blue” linewidth 1.000 size screen 0.018,14.000,45.000
set xrange [Xa:Xb]
set yrange [Ya:Yb]
set ytics 0.3
set pointsize 5
set xtics (“0” 0, '$-e^{-1/2}$' -0.606531, '$e^{-1/2}$' 0.606531, Xa, Xb)
set ytics (0, '0.97' 0.693147)
set key 1.43,2.7
plot f(x) lt 1 lc rgb “violet” lw 5 ti '$\displaystyle e^{-2x^2-1}-1$', '< echo 0 0' ti '' with points pt 11 ps 2 lc rgb "green" lw 2, '< echo 0.606531 .693147 ' ti '' with points pt 6 ps 1.5 lc rgb "gray" lw 2, '< echo -0.606531 0.693147 ' ti '' with points pt 6 ps 1.5 lc rgb "gray" lw 2 \end{gnuplot}` ma non funziona. Il problema, forse, è dovuto a keyval. Consigli?

Ho risolto così:

`
\newcommand{\w}{10cm,5cm}
\begin{gnuplot}[terminal=lua, terminaloptions = size \w]
set size 1,1
set border lt 1 lc rgb 'gray' lw 0.5
f(x)=log(1+exp(1)*x**2)
Xa = -2.5
Xb = 2.5
Ya = -0.3
Yb = 3
unset zeroaxis
unset xlabel
unset ylabel
set samples 200
set grid lt 3 lc rgb “gray” lw 0.5
set grid y2tics
set arrow 1 from Xa,0 to Xb,0,3 head back filled lt rgb “blue” linewidth 1.000 size screen 0.018,14.000,45.000
set arrow 2 from 0,Ya to 0,Yb,3 head back filled lt rgb “blue” linewidth 1.000 size screen 0.018,14.000,45.000
set xrange [Xa:Xb]
set yrange [Ya:Yb]
set ytics 0.3
set pointsize 5
set xtics (“0” 0, '$-e^{-1/2}$' -0.606531, '$e^{-1/2}$' 0.606531, Xa, Xb)
set ytics (0, '0.97' 0.693147)
set key 1.43,2.7
plot f(x) lt 1 lc rgb “violet” lw 5 ti '$\displaystyle e^{-2x^2-1}-1$', '< echo 0 0' ti '' with points pt 11 ps 2 lc rgb "green" lw 2, '< echo 0.606531 .693147 ' ti '' with points pt 6 ps 1.5 lc rgb "gray" lw 2, '< echo -0.606531 0.693147 ' ti '' with points pt 6 ps 1.5 lc rgb "gray" lw 2 \end{gnuplot}`