Produce table with contour_plot



Dear All,

The following

f(x,y) := x^2+y^2-1 ;
contour_plot(f(x,y),[x,-1.5,1.5],[y,-1.5,1.5],[gnuplot_preamble, "set cntrparam levels discrete 0.0"]) ;

produces a nice-looking plot of the unit circle.  However, if I thn
decide I want the (x,y) values on the contour in a
whitespace-separated table and issue

contour_plot(f(x,y),[x,-1.5,1.5],[y,-1.5,1.5],[gnuplot_preamble, "set table 'circletable.dat'; set cntrparam levels discrete 0.0"]) ;

the file circletable.dat is created, but is empty.  Any ideas, please?

-- 

Thanks,

Dan