Gnuplot ignoring missing data

[Dave Horsfall]

(I was wondering why this list was quiet; it seems I was unsubscribed for some 
reason.)

I don't know whether this is Macports-specific or upstream, but I like to 
identify my target before I open fire :-)

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