[newbie] zero file length when plotting (gnuplot-syntax)



I'm trying to make a pslatex-file from a plot as follows:

deltaurlrel(x):=1-1/(x*(1-x)*%beta+1);
relplots:makelist(deltaurlrel(x),%beta,[0.1,0.213,0.444,1,4.545]);
plot2d(relplots,[x,0.01,1],[legend,"beta0.1","beta0.213","beta0.444","beta1","beta4.545"],[gnuplot_preamble,"set terminal pslatex; set output 'plotrel.tex';"]);

unfortunately the resulting file "plotrel.tex' is empty
can anyone here tell me what (syntax?) error I'm making here?

hugo