gnuplot and filledcurves



  Hi all! I'm trying to plot a curve with filledcurves gnuplot option,
but without any success. What i've tried:

set_plot_options([gnuplot_curve_styles,["with filledcurves closed"]]);
plot2d(sin(x),[x,0,2*%pi]);

but what i get it's not different from the usual sin(x) plot. What i'm
doing wrong?

thanks,
  Giovanni