$lst_tit leveldata$lst_titend$type_both
$lst_alias levelpoints
$(lst_syntax)leveldata size $emph xsize,ysize$emphend
ranges $emph x1,x2,y1,y2$emphend function $emph f(x,y)$emphend
[levels $emph l1,l2,...$emphend]</span>
$lst_mean Computes coordinates of points on the level curve of
$emph f(x,y)$emphend, at levels $emph l1,l2,...$emphend (defaults to one
level 0). <p>
The computation is made from $emph (x1,y1)$emphend to
$emph (x2,y2)$emphend, and points are computed as integer positions in a
picture with size $emph xsize,ysize$emphend. </p><p>
Order of the fields is not important. All the fields except levels are
mandatory.
</p>