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Question

I am trying to plot a graph using gnuplot. I have six text files. Each text file contains two columns. The first column represents time in seconds (a floating point number). The second one is a sequence number. I want to plot the graph of time vs. sequence number in a single graph for all six files. I am using this file to do that.

set terminal png
set output 'akamai.png'
set xdata time
set timefmt "%S"
set xlabel "time"
set autoscale
set ylabel "highest seq number"
set format y "%s"
set title "seq number over time"
set key reverse Left outside
set grid
set style data linespoints
plot "print_1012720" using 1:2 title "Flow 1", \
plot "print_1058167" using 1:2 title "Flow 2", \
plot "print_193548"  using 1:2 title "Flow 3", \ 
plot "print_401125"  using 1:2 title "Flow 4", \
plot "print_401275"  using 1:2 title "Flow 5", \
plot "print_401276"  using 1:2 title "Flow 6"

Where my files are:

• print_1012720
• print_1058167
• print_193548
• print_401125
• print_401275
• print_401276

It is giving a strange error as below:

"plot.plt", line 24: undefined variable: plot

Am I doing something wrong? Is it possible to plot the input data from different files in the same graph?

Answer

You may find that gnuplot's for loops are useful in this case, if you adjust your filenames or graph titles appropriately.

e.g.

filenames = "first second third fourth fifth"
plot for [file in filenames] file."dat" using 1:2 with lines

and

filename(n) = sprintf("file_%d", n)
plot for [i=1:10] filename(i) using 1:2 with lines