CCL: How to create a b&w contour plot containing a cutout

 Sent to CCL by: "Ray Merewether" [Ray_Merewether*o*]
 In Matlab, you can use NaN (Not A Number) to cut holes in surf(),
 surfc() and contour() plots.  Octave should be similar.
 -----Original Message-----
 > From: []
 Sent: Friday, March 24, 2006 2:08 AM
 To: Ray Merewether
 Subject: CCL: How to create a b&w contour plot containing a cutout
 Sent to CCL by: Anselm.Horn^
 Dear all,
 I'm sorry, if this is a bit off-topic.
 When looking for a way to visualize the electrostatic potential of
 systems, one very often finds black&white contour plots, one in the
 one above (e.g. Ford&Wang, J. Comput. Chem. 1993, 14, 1101-1111). Does
 anybody know a program that could create such graphics from 2D raw data?
 Of course, I tried gnuplot, but I faced the following problem:
 The property values in the plane near the atomic cores were omitted in
 above paper, and in the contour plot graphic the lewis structure of the
 molecule is shown there.
 However, I cannot tell gnuplot to omit the respective data, because it
 needs a complete set of rows and columns. On the other hand, if one
 sets the values, that are to omit, to a very high or low constant, the
 countour lines near the molecular border are probably not correctly
 calculated (or am I wrong?).
 The same problems arise with xmgrace, unfortunately.
 Any hints are welcome!
 Best regards,
 Anselm Horn
 Friedrich-Alexander-Universitaet Erlangen-Nuernberg