Command and Script to Re-Read a File in Gnuplot

Command and Script to re-read a file in gnuplot

Change your command to the following:

gnuplot -persist -e "plot 'data.dat' using 1:2 with lines ,'' using 1:3 with lines" loop.plt

This plots columns 1 and 2 and columns 1 and 3 using lines

how to read a script (which is stored as a file) in gnuplot

To run a script called 'filename', you can type

gnuplot "filename"

or from within an interactive gnuplot environment you can load a script file by typing

load "filename"

Edit: As per Gabriel's comment below, you can let the plot generated by a script persist and close your gnuplot session by using the -p or --persist option. Do note that the plot which persists won't have any interactive features like zooming/scrolling.

gnuplot -p "filename"

More info available on the gnuplot official documentation(page 22)

How to automatically replot a graph every few seconds in gnuplot?

Make a script with a loop:

while (1) {
    plot "a.dat"
    pause 1      # waiting time in seconds
}

Execute it with gnuplot script.gp.

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For purposes of code structure and debugging, you might prefer the following alternative:

plot "a.dat"

while (1) {
    replot
    pause 1
}

This has the advantage that you do not have to put a complicated plot command inside the loop and do not suffer from incorrect line numbers for the plot command in error messages (that happen in at least some version of Gnuplot).

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Finally, if your Gnuplot is so old that it does not yet support loops, there is the alternative:

plot "a.dat"

pause 1
reread

With reread making the script interpreter jump to the beginning of the file again.

Parse and plot data received from log-file on-the-fly

Here are two ways for plotting data on-the-fly.

Looping with gnuplot

You must call plot over and over again, the data is preprocessed by an external script. The minimal gnuplot script filter.gp is:

while (1) {
    plot '< ./myscript.pl' using 2:1
    pause 1
}

To stop this, hit Ctrl+C.

The Perl script for the preprocessing may look like the following myscript.pl:

#!/usr/bin/perl
use strict;
use warnings;

my $path = "file.log";   
my @grepped;
my $t = 0;
open(INFILE,"< $path") or die "$! \n";

while (my $line = <INFILE>) {
    if ($line =~ m{^Time = (\d+)}){
        $t = $1;
    };

    if ($line =~ m{^Errors: local = (\d+), global = (\d+)}){
        print "$t\t$1\t$2\n";
    };
};
close(INFILE);

Just run it with gnuplot filter.gp.

To make it more configurable, one can change the script to use a variable which is passed to gnuplot via the command line:

while (1) {
    plot '< ./myscript.pl -f '.path using 2:1
    pause 1
}

or use reread for this:

plot '< ./myscript.pl -f '.path using 2:1
pause 1
reread

Call this script with gnuplot -e "path='file.log';" filtermod.gp.

That works, but would filters the complete file over and over again.

Piping from Perl to gnuplot

Here is a Perl script, which basically works for me, but its my first real Perl script, so there may be some nonideal parts. Feel free to comment on that.

#!/usr/bin/perl
use strict;
use warnings;

my $path = "file.log";   
my @grepped;
my $switch = "off";

open(my $gp, "| gnuplot -persist") or die "$! \n";
$gp->autoflush(0);

use File::Tail;
my $file = File::Tail->new(name=>$path, maxinterval=>1, tail=>-1);

while (defined(my $line= $file->read)) {
    if ($line =~ m{^Time = (\d+)}){
        push(@grepped,"$1\t");
    };

    if ($line =~ m{^Errors: local = (\d+), global = (\d+)}){
        push(@grepped,"$1\t");
        push(@grepped,"$2\n");
        $switch = "refresh";
    };

    if ($switch eq "refresh") {
        print $gp <<"GNU_EOF";
plot '-' using 2:1
@grepped
e
GNU_EOF
        $gp->flush;
        $switch = "off"; 
    };
    Time::HiRes::sleep(0.1);
};

What I found to be important here is

1. Looping over a changing file.
2. The arrangement of the autoflush and flush.
3. The sleep to allow gnuplot to process the data properly.

That worked for a very small test data file. Don't know if it will for a larger one as well, but should help you a bit further.

Ubuntu - gnuplot reread deselecting text

You can use a different terminal (pdf, eps, etc.) and keep the output open in evince, which refreshes automatically. This worked for me when I used to work in Ubuntu.

set term pdfcairo
set output 'dynamics.pdf'
...

As for why this is happening: my thought is that if you are running a very new version of Ubuntu, X may not be playing nice with Mir. Otherwise it's not very clear to me; it may be worth filing as a bug report.

Keep Gnuplot auto refresh window inactive

This depends on what terminal you're using. wxt, x11 and qt support a noraise option:

set term x11 1 noraise

This should allow it to stay in the background.

Reading a data file with multiple blocks as one coherent data file

A little cheat with awk:

plot "<awk -F'[ ]' '/\\S/ {printf(\"%f %f\\n\",$1,$2)}' <data.dat "  w l

will ignore blank lines. (\S <=> 'non-whitespace')

NOTE

-F'[ ]' and printf are overinsurances:

plot "<awk  '/\\S/ {print $0}' <data.dat "  w l

is almost as good as.

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