=head1 NAME

feedGnuplot - A pipe-oriented frontend to Gnuplot

=head1 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

=head1 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. The C<awk> command generates some data to
plot and the C<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
C<--extracmds> and C<--curvestyle> options. Arbitrary gnuplot commands can be
passed in with C<--extracmds>. For example, to turn off the grid, pass in
C<--extracmds 'unset grid'>. As many of these options as needed can be pased
in. To add arbitrary curve styles, use C<--curvestyle extrastyle>. Pass these
more than once to affect more than one curve. To apply an extra style to I<all>
the curves, pass in C<--curvestyleall extrastyle>.

=head2 Data formats

By default, each value present in the incoming data represents a distinct data
point, as demonstrated in the above example (we had 10 numbers in the input and
10 points in the plot). If requested, the script supports more sophisticated
interpretation of input data

=head3 Domain selection

If C<--domain> is passed in, the first value on each line of input is
interpreted as the I<X>-value for the rest of the data on that line. Without
C<--domain> the I<X>-value is the line number, and the first value on a line is
a plain data point like the others. Default is C<--nodomain>. Thus the example
above produces 2 curves, with B<1,2,3,4,5> as the I<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 B<2,4,6,8,10> as the I<X>-values. As many points as
desired can appear on a single line, but all points on a line are associated
with the I<X>-value at the start of that line.

=head3 Curve indexing

By default, each column represents a separate curve. This is fine unless sparse
data is to be plotted. With the C<--dataid> option, each point is represented by
2 values: a string identifying the curve, and the value itself. If we add
C<--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 C<awk>, is B<2,4,6,8,10>. These are interpreted as the IDs of the curves to
be plotted. The C<--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. C<--domain> can be used in
conjunction with C<--dataid>.

=head3 Multi-value style support

Depending on how gnuplot is plotting the data, more than one value may be needed
to represent a single point. For example, the script has support to plot all the
data with C<--circles>. This requires a radius to be specified for each point in
addition to the position of the point. Thus, when plotting with C<--circles>, 2
numbers are read for each data point instead of 1. A similar situation exists
with C<--colormap> where each point contains the position I<and> the
color. There are other gnuplot styles that require more data (such as error
bars), but none of these are directly supported by the script. They can still be
used, though, by specifying the specific style with C<--curvestyle>, and
specifying how many extra values are needed for each point with
C<--extraValuesPerPoint extra>. C<--extraValuesPerPoint> is ONLY needed for the
styles not explicitly supported; supported styles set that variable
automatically.

=head3 3D data

To plot 3D data, pass in C<--3d>. C<--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 (I<Z> as a function of I<X> and I<Y>
instead of I<Y> as a function of I<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.

=head2 Real-time streaming data

To plot real-time data, pass in the C<--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 I<all> the data),
C<--xlen windowsize> can be given. This will create an constantly-updating,
scrolling view of the recent past. C<windowsize> should be replaced by the
desired length of the domain window to plot, in domain units (passed-in values
if C<--domain> or line numbers otherwise).

=head2 Hardcopy output

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

=head2 Self-plotting data files

This script can be used to enable self-plotting data files. There are 2 ways of
doing this: with a shebang (#!) or with inline perl data.

=head3 Self-plotting data with a #!

A self-plotting, executable data file C<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.

=head3 Self-plotting data with perl inline data

Perl supports storing data and code in the same file. This can also be used to
create self-plotting files:

 $ cat plotdata.pl
 #!/usr/bin/perl
 use strict;
 use warnings;

 open PLOT, "| feedGnuplot --lines --points" or die "Couldn't open plotting pipe";
 while( <DATA> )
 {
   my @xy = split;
   print PLOT "@xy\n";
 }
 __DATA__
 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 especially useful if the logged data is not in a format directly
supported by feedGnuplot. Raw data can be stored after the __DATA__ directive,
with a small perl script to manipulate the data into a useable format and send
it to the plotter.

=head2 Further help

All the options are described with

 $ feedGnuplot --help

=head1 ACKNOWLEDGEMENT

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

=head1 REPOSITORY

L<https://github.com/dkogan/feedgnuplot>

=head1 AUTHOR

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

=head1 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.

=cut