Gnuplot plot specific lines from data file

2
votes

I have a data file with 24 lines and 3 columns. How can I plot only the data from specific lines, e.g. 3,7,9,14,18,21? Now I use the following command

plot 'xy.dat' using 0:2:3:xticlabels(1) with boxerrorbars ls 2

which plots all 24 lines.

I tried the every command but couldn't figure out a way that works.

2
gnuplot

2 Answers

3
votes

Untested, but something like this

plot "<(sed -n -e 3p -e 7p -e 9p xy.dat)" using ...

Another option may be to annotate your datafile, if as it seems, it contains multiple datasets. Let's say you created your datafile like this:

1 2 3
2 1 3 # SetA
2 7 3 # SetB
2 2 1 # SetA SetB SetC

Then if you wanted just SetA you would use this sed command in the plot statement

sed -ne '/SetA/s/#.*//p' xy.dat
2 1 3
2 2 1

That says..."in general, don't print anything (-n), but, if you do see a line containing SetA, delete the hash sign and everything after it and print the line".

or if you wanted SetB, you would use

sed -ne '/SetB/s/#.*//p' xy.dat
2 7 3
2 2 1

or if you wanted the whole data file, but stripped of our comments

sed -e 's/#.*//' xy.dat

If you wanted SetB and SetC, use

sed -ne '/Set[BC]/s/#.*//p' xy.dat
2 7 3 
2 2 1
2
votes

If the lines you want have something in common that you can evaluate, e.g. the label in column 1 begins with an "a"

 plot dataf using (strcol(1)[1:1] eq "a" ? $0 : NaN):2:xticslabel(1)

you can just skip these lines by letting the using statement return "NaN".

This here is an ugly hack you can use in case the desired line numbers are just arbitrary:

linnum = " 1 3 7 12 16 21 "
plot dataf using (strstrt(linnum," ".int($0)." ") != 0 ? $0 : NaN):2

strstrt(a,b) returns the position of string b in string a, zero if it does not appear. I add the two spaces to make the line numbers unique.

But I would recommend using an external program to preprocess the data in that case, see the other answer.