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Date: Wed, 7 Mar 2018 10:33:57 -0800 (PST)
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Subject: Missing points in multi line plot not being omitted
From: Marius Schamschula <mschamschula@gmail.com>
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Xref: csiph.com comp.graphics.apps.gnuplot:3900

I'm trying to make a plot of wind speed and wind gusts. The data for wind g=
usts is not continuous. If I use datafile missing on the wind gust data by =
itself, things work as expectedly, but if I try to plot gusts along with wi=
nd speed, gusts data are shown for times where there is no data. The plot o=
mits gusts data at the beginning and end, but in the middle line segments a=
re drawn where they should not. For example

set datafile missing NaN
set grid
set time
set xdata time
set timefmt "%Y-%m-%d:%H:%M:%S"
unset timestamp
plot '-' u 1:2 t 'Wind' w lines lt rgb "blue", '-' u 1:3 t 'Gust' w lines
2018-03-07:12:53:00 12 18
2018-03-07:11:53:00 12 ?
2018-03-07:10:53:00 12 23
2018-03-07:09:53:00 20 28
2018-03-07:08:53:00 17 ?
2018-03-07:07:53:00 13 23
2018-03-07:06:53:00 15 28
2018-03-07:05:53:00 15 29
2018-03-07:04:53:00 17 26
2018-03-07:02:53:00 9 ?
2018-03-07:01:53:00 12 ?
2018-03-07:00:53:00 16 ?
2018-03-06:23:53:00 16 24
2018-03-06:22:53:00 16 29
2018-03-06:21:53:00 13 22
2018-03-06:20:53:00 15 22
2018-03-06:19:53:00 14 21
2018-03-06:18:53:00 13 20
2018-03-06:17:53:00 10 17
2018-03-06:16:53:00 10 ?
2018-03-06:15:53:00 7 ?
2018-03-06:14:53:00 12 ?
2018-03-06:13:53:00 12 ?
e
2018-03-07:12:53:00 12 18
2018-03-07:11:53:00 12 ?
2018-03-07:10:53:00 12 23
2018-03-07:09:53:00 20 28
2018-03-07:08:53:00 17 ?
2018-03-07:07:53:00 13 23
2018-03-07:06:53:00 15 28
2018-03-07:05:53:00 15 29
2018-03-07:04:53:00 17 26
2018-03-07:02:53:00 9 ?
2018-03-07:01:53:00 12 ?
2018-03-07:00:53:00 16 ?
2018-03-06:23:53:00 16 24
2018-03-06:22:53:00 16 29
2018-03-06:21:53:00 13 22
2018-03-06:20:53:00 15 22
2018-03-06:19:53:00 14 21
2018-03-06:18:53:00 13 20
2018-03-06:17:53:00 10 17
2018-03-06:16:53:00 10 ?
2018-03-06:15:53:00 7 ?
2018-03-06:14:53:00 12 ?
2018-03-06:13:53:00 12 ?
e

The data is normally read from a temporary file, with additional formatting=
 applied. A full example is

http://wx.aamu.edu/Images/mkpng.php?cws+KHSV

This is generated real time, so sometimes there isn't any wind gust data, o=
r there are gusts over the whole time period.