Re: Missing/invalid data points

[Ethan M. <merritt@u.washington.edu>]

On Monday 28 August 2006 02:52 pm, Ethan Merritt wrote:
>
> However, I think we very definitely should fix the currently broken
> behavior of
> 	splot 'foo' using 1:2:3
> in the presence of nonsense or NaN strings

Here is the essence of the problem:

# Data file junk.dat
0.1 10 1.111
0.2 20 2.222
0.3 NaN 3.333
0.4 40 4.444



gnuplot> splot 'junk.dat' using 1:2:3 with pm3d

#IsoCurve 0, 3 points
#x y z type
 0.1  10  1.111 i
 0.2  20  2.222 i
 0.4  40  4.444 i

gnuplot> splot 'junk.dat' using ($1):($2):($3) with pm3d

#IsoCurve 0, 4 points
#x y z type
 0.1  10  1.111 i
 0.2  20  2.222 i
 0  0  0 u
 0.4  40  4.444 i


The first case (using 1:2:3) omits the line altogether,
which unfortunately messes up the gridding and produces
a distorted surface.

The second case keeps the point, marking it as undefined.
That is better, but it would be better yet if the information
stored was
   0.3 NaN 3.33 u
If nothing else, that would allow the tabular output line
to match the original input line.  Beyond that, the extra
info may be of use in auto-scaling the axes, auto-gridding 
(not in this case, but if it were the Z value that was bad),
interpolation of color values, and probably things I haven't
thought of.


-- 
Ethan A Merritt
Biomolecular Structure Center
University of Washington, Seattle WA