/ 
feedGnuplot-1.00
River stage zero No dependents
/ feedGnuplot

NAME

feedGnuplot - A pipe-oriented frontend to Gnuplot

SYNOPSIS

Simple plotting of stored data:

$ seq 5 | awk '{print 2*$1, $1*$1}'
2 1
4 4
6 9
8 16
10 25

$ seq 5 | awk '{print 2*$1, $1*$1}' |
  feedGnuplot --lines --points --legend "data 0" --title "Test plot" --y2 1

Simple real-time plotting example: plot how much data is received on the wlan0 network interface in bytes/second (uses bash, awk and Linux):

$ while true; do sleep 1; cat /proc/net/dev; done |
  awk '/wlan0/ {if(b) {print $2-b; fflush()} b=$2}' |
  feedGnuplot --lines --stream --xlen 10 --ylabel 'Bytes/sec' --xlabel seconds

DESCRIPTION

This is a flexible, command-line-oriented frontend to Gnuplot. It creates plots from data coming in on STDIN or given in a filename passed on the commandline. Various data representations are supported, as is hardcopy output and streaming display of live data. A simple example:

$ seq 5 | awk '{print 2*$1, $1*$1}' | feedGnuplot

You should see a plot with two curves: one on the y1 axis (left) and the other on the y2 axis (right). The plots should have a legend and a title. The awk command generates some data to plot and the feedGnuplot reads it in from STDIN and generates the plot. The <awk> invocation is just an example; more interesting things would be plotted in normal usage. None of the commandline-options are required for the most basic plotting. Input parsing is flexible; every line need not have the same number of points. New curves will be created as needed.

The most commonly used functionality of gnuplot is supported directly by the script. Anything not directly supported can still be done with the --extracmds and --curvestyle options.

Data formats

Domain selection

There are 2 main commandline options to control the interpretation of the input data. If --domain is passed in, the first value on each line of input is interpreted as the X-value for the rest of the data on that line. Without --domain the X-value is the line number, and the first value on a line is a plain data point like the others. Default is --nodomain. Thus the example above produced 2 curves, with 1,2,3,4,5 as the X-values. If we run the same command with --domain:

$ seq 5 | awk '{print 2*$1, $1*$1}' | feedGnuplot --domain

we get only 1 curve, with 2,4,6,8,10 as the X-values. As many points as desired can appear on a single line, but all points on a line are associated with the X-value at the start of that line.

Curve indexing

By default, each column represents a separate curve. This works unless sparse data is to be plotted. With the --dataid option, each point is represented by 2 values: a string identifying the curve, and the value itself. If we add --dataid to the original example:

$ seq 5 | awk '{print 2*$1, $1*$1}' | feedGnuplot --dataid --autolegend

we get 5 different curves with one point in each. The first column, as produced by awk, is 2,4,6,8,10. These are interpreted as the IDs of the curves to be plotted. The --autolegend option adds a legend using the given IDs to label the curves. The IDs need not be numbers; generic strings are accepted. As many points as desired can appear on a single line. --domain can be used in conjunction with --dataid.

3D data

To plot 3D data, pass in --3d (for 3D curves) or --colormap (top-down view, color encoding Z). --domain MUST be given when plotting 3D data to avoid domain ambiguity. If 3D data is being plotted, there are by definition 2 domain values instead of one (Z as a function of X and Y instead of Y as a function of X). Thus the first 2 values on each line are interpreted as the domain instead of just 1. The rest of the processing happens the same way as before.

Real-time streaming data

To plot display realtime data, pass in the --stream option. Data will then be plotted as it is received, with the refresh rate limited to 1Hz (currently hard-coded). To plot only the most recent data (instead of all the data), --xlen windowsize can be given. This will create an constantly-updating, scrolling view of the recent past. The windowsize is given in domain units (passed-in values if --domain or line numbers otherwise).

Hardcopy output

The script is able to produce hardcopy output with --hardcopy outputfile. The output type is inferred from the filename with .ps, .eps, .pdf and .png currently supported.

Self-plotting data files

This script can be used to create self-plotting data files. A self-plotting, executable data file data is formatted as

$ cat data
#!/usr/bin/feedGnuplot --lines --points
2 1
4 4
6 9
8 16
10 25
12 36
14 49
16 64
18 81
20 100
22 121
24 144
26 169
28 196
30 225

This is the shebang (#!) line followed by the data, formatted as before. The data file can be plotted simply with

$ ./data

The caveats here are that on Linux the whole #! line is limited to 127 charaters and that the full path to feedGnuplot must be given. The 127 character limit is a serious limitation, but this can likely be resolved with a kernel patch. I have only tried on Linux 2.6.

Further help

All the options are described with

$ feedGnuplot --help

ACKNOWLEDGEMENT

This program is originally based on the driveGnuPlots.pl script from Thanassis Tsiodras. It is available from his site at http://users.softlab.ece.ntua.gr/~ttsiod/gnuplotStreaming.html

REPOSITORY

https://github.com/dkogan/feedgnuplot

AUTHOR

Dima Kogan, <dkogan at cds.caltech.edu>

LICENSE AND COPYRIGHT

Copyright 2011 Dima Kogan.

This program is free software; you can redistribute it and/or modify it under the terms of either: the GNU General Public License as published by the Free Software Foundation; or the Artistic License.

See http://dev.perl.org/licenses/ for more information.