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Gnuplot reads weather data from a huge file called file.dat and plots the weather data for a given date and time.

But if there is no data for the given date and time (xrange), gnuplot crashes.

How can I tell gnuplot, if there is no data for a given date and time, display a text in the output image?

("There is no data available, I am sorry")

The error, if there is no data available:

line 0: all points y2 value undefined!

The script.dem file, which is loaded by gnuplot:

reset


#SET TERMINAL
set term svg
set output 'temp-verlauf.svg'
set title "Temperaturverlauf"

#Axes label
set xlabel "Messzeitpunkt"
set ylabel "Luftfeuchte/Temperatur"
set y2label "Luftdruck"

#Axis setup
set xdata time # x-Achse wird im Datums/Zeitformat skaliert
set timefmt "%d.%m.%Y\t%H:%M:%S" # Format Zeitangaben yyyy.mm.dd_hh:mm:ss
set format x "%H:%M" # Format für die Achsenbeschriftung


#Axis ranges
set yrange [0:60] # die y-Achse geht von:bis

#Tics
set ytics nomirror
set y2tics nomirror

#OTHER
set datafile separator "\t"
set xrange ["06.11.2014 14:00:00":"07.11.2014   21:00:00"]

plot \
"file.dat" every 10 using 1:5 title "Luftfeuchte" with lines, \
"file.dat" every 10 using 1:6 title "Temperatur" with lines, \
"file.dat" every 10 using 1:7 title "Luftdruck" with lines axes x1y2, \
"file.dat" every 10 using 1:17 title "Niederschlagsintensitaet Synop (4677)" with lines

EDIT

Thanks to user "bibi".
He had the good idea to let gnuplot plot -1 to have data if there is nothing avaible in file.dat.

The script will look like that:

reset


#SET TERMINAL
set term svg
set output 'temp-verlauf.svg'
set title "Temperaturverlauf"

#Axes label
set xlabel "Messzeitpunkt"
set ylabel "Luftfeuchte/Temperatur"
set y2label "Luftdruck"

#Axis setup
set xdata time # x-Achse wird im Datums/Zeitformat skaliert
set timefmt "%d.%m.%Y\t%H:%M:%S" # Format Zeitangaben yyyy.mm.dd_hh:mm:ss
set format x "%H:%M" # Format für die Achsenbeschriftung


#Axis ranges
set yrange [0:60] # die y-Achse geht von:bis

#Tics
set ytics nomirror
set y2tics nomirror

#OTHER
set datafile separator "\t"
set xrange ["06.11.2014 14:00:00":"07.11.2014   21:00:00"]

plot \
-1 axes x1y2, \
-1 axes x1y1, \
"file.dat" every 10 using 1:5 title "Luftfeuchte" with lines, \
"file.dat" every 10 using 1:6 title "Temperatur" with lines, \
"file.dat" every 10 using 1:7 title "Luftdruck" with lines axes x1y2, \
"file.dat" every 10 using 1:17 title "Niederschlagsintensitaet Synop (4677)" with lines
user5206643
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2 Answers2

2

The simplest solution it came to my mind is to draw an horizontal line outside the plotting region (-1 is ok since you have set yrange [0:60]):

plot \
-1, \
"file.dat" every 10 using 1:5 title "Luftfeuchte" with lines, \
"file.dat" every 10 using 1:6 title "Temperatur" with lines, \
"file.dat" every 10 using 1:7 title "Luftdruck" with lines axes x1y2, \
"file.dat" every 10 using 1:17 title "Niederschlagsintensitaet Synop (4677)" with lines

Moreover the gnuplot internal variable GPVAL_ERRNO will be non-zero if something weird happened, you might check that and print a banner on screen.

bibi
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  • This is a good solution. Not the best ,because the -1 line. But yes, thank you very much. But i do -1 axes x1y2, \ -1 axes x1y1, \ to have data in all axes. – user5206643 Jan 02 '16 at 16:52
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Your data in your file is double. So after plotting once it jumps back to the start and plots everything another time on top of the first plot.

Took me a couple of hours to figure out. :)

Rain
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martinimartin
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