Re: Gnuplot ignoring missing data (fwd)

I think you misunderstand what "set datafile missing" does -- at
least in the current gnuplot version. To quote from "help set
datafile missing":

  Gnuplot makes a distinction between missing data and invalid
  data (e.g. "NaN", 1/0.). For example invalid data causes a gap
  in a line drawn through sequential data points; missing data
  does not.

The help also notes missing/invalid handling changed between v4
and v5, so StackOverflow's advice may have been correct at one
time.

(I don't know why nobody is replying... I certainly don't have
any special knowledge in this area.)


Dave Horsfall <[email protected]> said (on 2019/09/16):
> Was my question too hard to answer, or merely mis-phrased?  I simply want 
> to know whether I have misunderstood the meaning of "set datafile missing" 
> or should I be reporting it as a Gnuplot bug?
> 
> I don't like reporting bugs if it turns out to be my fault...
> 
> -- Dave
> 
> ---------- Forwarded message ----------
> Odd; I just noticed that another of my graphs has a discontinuity at missing 
> data, yet I don't have the "set datafile missing 'x'" line, so what on earth 
> could be wrong?  What have I not understood about missing data?
> 
> Taking that directive out of spamlog.gp indeed shows a discontinuity (see 
> www.horsfall.org/spamlog-1.pdf) so something is definitely fishy here...
> 
> -- Dave
> 
> ---------- Forwarded message ----------
> Mac Sierra + latest patches (it won't go any further), Gnuplot 5.2 p6.
> 
> Have a look at www.horsfall.org/spamlog.pdf and note the weirdness at the end; 
> there is missing data there thanks to my ISP cutting my fibre and taking ages 
> to fix it (great anti-spam measure, I suppose).
> 
> In my spamlog.gp, I have:
> 
>      set datafile    missing "x"
>      ...
>      plot datafile using 1:($2)       lt rgb "red"    title 'Reject', \
>      ...
> 
> Sample line from spamlog.dat:
> 
>      2019/04/26      x x x x x x x x x
>      (Actually tabs, not spaces)
> 
> Have I misunderstood what "missing" means?  It's been a while since I studied 
> stats...  My understanding is just that: missing data, hence leave a hole in 
> your graph (indistinguishable from zero in my case, but I can handle that).
> 
> A message on StackOverflow also says that the above should work and not draw a 
> line across it (not that I trust StackOverflow anyway), but that's exactly what 
> Gnuplot is doing.
> 
> Thanks.
> 
> -- Dave


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