Gnuplot date/time in x axis

Question

I have a quick question regarding dates and times in x-axis in GNUPLOT. I'll let the code do the talking:

This is my data:

#Time   Data in Data out "2013-07-22 15:59:00"   6286    3730 "2013-07-22 15:58:00"   10695   14589 "2013-07-22 15:57:00"   17868   26464 "2013-07-22 15:56:00"   18880   34012 "2013-07-22 15:55:00"   19206   41192 "2013-07-22 15:54:00"   20365   43218 "2013-07-22 15:53:00"   18459   39298 "2013-07-22 15:52:00"   3420    4686 "2013-07-22 15:51:00"   3256    4942 

And this is the code that is generating the graph:

gnuplot> set title "Data usage over the last 24 hours" gnuplot> unset multiplot gnuplot> set xdata time gnuplot> set style data lines   gnuplot> set term png Terminal type set to 'png' Options are 'nocrop font "arial,12" fontscale 1.0 size 640,480 ' gnuplot> set timefmt "%Y-%m-%d %H:%M:%S" gnuplot> set format x "%m-%d\n%H:%M" gnuplot> set xlabel "Time" gnuplot> set ylabel "Traffic"  gnuplot> set autoscale y   gnuplot> set xrange ["2013-07-21 16:00":"2013-07-22 16:00"] gnuplot> set output "datausage.png" gnuplot> plot "C:\\Users\\blah\\Desktop\\plot.tmp" using 1:2 t "inbound" w lines, "C:\\Users\\blah\\Desktop\\plot.tmp" u 1:3 t "outbound" w lines                                                                                                                                                                  ^          all points y value undefined! 

Is the problem the space in between date and time in the x-axis? If not, what do you think could be the problem?

Answer 1

Gnuplot doesn't actually expect time data to be in quotes, so you have to tell it:

set timefmt '"%Y-%m-%d %H:%M:%S"' 

You can put the double quotes inside single quotes as I did here, or escape the quotes:

set timefmt "\"%Y-%m-%d %H:%M:%S\"" 

the same applies to your xrange specification:

set xrange ['"2013-07-21 16:00"':'"2013-07-22 16:00"'] 

If you delete the quotes in the data file, then you can use the formatting you originally had, except the column numbers will be shifted over by 1 since the date takes up two columns without the quotes.