Awk not working in the second part or sub plot of the gnuplot command

Question

Through gnuplot I am trying to print an average line on the graph, but it is not working, if I use awk command in the second part or second sub-plot command like this

plot "iops.1.log" using ($1/1000):2 with lines title "job 1",\
     "<awk '{sum += $2} END {print sum/NR}' iops.1.log" with lines title "avg iops"

But if I give the value directly that I get if I run the same awk command on the bash command line, the line gets printed like this.

plot "iops.1.log" using ($1/1000):2 with lines title "job 1",\
     4590 with lines title "avg iops"

The line above prints the running average line in the graph using just one value(4590) in the second subplot

What is exactly happening and why is must not be working?

meuh · Accepted Answer · 2020-04-30 15:29:55Z

2

It might be a bug, but luckily you can calculate the average y value within gnuplot without needing awk:

stats "iops.1.log" nooutput
ave=STATS_sum_y/STATS_records
plot "iops.1.log" using ($1/1000):2 with lines title "job 1",\
 ave with lines title "avg iops"

answered Apr 30, 2020 at 15:29

meuh

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Christoph · Accepted Answer · 2020-04-30 17:47:21Z

1

When plotting with plot "<awk ..." and the awk-command returns a single number, you effectively have a data file with a single number. In contrast to this, invoking plot 4560 plots a function, which is then plotted over the full x-range.

If you want to stick with awk, or simply as explanation of an alternative, you can do

avg = system("<awk '{sum += $2} END {print sum/NR}' iops.1.log")
plot "iops.1.log" using ($1/1000):2 with lines title "job 1",\
     int(avg) with lines title "avg iops"

answered Apr 30, 2020 at 17:47

Christoph

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Friedrich -- Слава Україні · Accepted Answer · 2020-04-30 18:27:10Z

1

The construct "<..." gives a piped file. To calculate and plot the mean, you can use back tics:

plot "iops.1.log" using ($1/1000):2 with lines title "job 1",\
    `awk '{sum += $2} END {print sum/NR}' iops.1.log` with lines title "avg iops"

answered Apr 30, 2020 at 18:27

Friedrich -- Слава Україні

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