Plotting 2 series from one data set in gnuplot

Question

I have the following data file:

Time;Server;Hits
2011.05.05 12:00:01;Server1;12
2011.05.05 12:00:01;Server2;10
2011.05.05 12:00:02;Server1;2
2011.05.05 12:00:02;Server2;4

So, far I have come up with the following gnuplot script:

set datafile separator ";"
set autoscale
set xdata time
set timefmt "%Y.%m.%d %H:%M:%S"
set xtics rotate 
set term png 
set output "hits.png"
set style fill solid 0.5
plot "hits.log" using 1:3 title 'Hits'

But that one plots data from both servers on the same graph as one data series. How do I make gnuplot to display 2 data series: one for each server?

Andrey Adamovich · Accepted Answer · 2011-05-05 11:46:01Z

5

I found a soluton myself:

plot "hits.log" using 1:(stringcolumn(2) eq "Server1" ? $3 : 1/0) title 'Server1' with lines,\
     "hits.log" using 1:(stringcolumn(2) eq "Server2" ? $3 : 1/0) title 'Server2' with lines

answered May 5, 2011 at 11:46

Andrey Adamovich

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4 Comments

neillb Over a year ago

Here's info (for others) on the "1/0" core of this solution: From the manual "The integer expression "1/0" may be used to generate an "undefined" flag, which causes a point to ignored; the ternary operator gives an example. Or you can use the pre-defined variable NaN to achieve the same result."

Andrey Adamovich Over a year ago

@nellib, do you know if it is possible to plot several series if number of series is not known beforehand? i.e. Server1 .. ServerN where is N is variable.

neillb Over a year ago

I don't know a nice way. You could pre-process the file to sort and space it into a data set for each server, or of course to your own solution you could add plot clauses one for each possible server (yuck!) assuming you know your max N and it's not huge. In the past for this I have written a (ruby) script to inspect the data file and generate the gnuplot plot command accordingly. There's likely a better way. You could add the "up to variable N" problem to your original question (as a bonus part) so more people see it.

Andrey Adamovich Over a year ago

@nellib, thanks for your comment. I did something similar eventually by creating a perl script.

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