=head1 NAME

feedgnuplot - 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 0 "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 |
   gawk '/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
C<awk> invocation is just an example; more interesting things would be plotted
in normal usage. No 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 passed
in. To add arbitrary curve styles, use C<--curvestyle curveID 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 original example above (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 original
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.

=head3 Special data commands

Other than the raw data, 2 special commands are interpreted if they appear in
the input. These are C<replot> and C<clear>. If a line of data begins with
C<replot> and we're plotting in realtime with C<--stream>, the plot will be
refreshed immediately. If a line of data begins with C<clear>, the plot is
cleared, to be re-filled with any data following the C<clear>.

=head2 Real-time streaming data

To plot real-time data, pass in the C<--stream [refreshperiod]> option. Data
will then be plotted as it is received. The plot will be updated every
C<refreshperiod> seconds. If the period isn't specified, a 1Hz refresh rate is
used. To refresh at specific intervals indicated by the data, set the
refreshperiod to 0 or to 'trigger'. The plot will then I<only> be refreshed when
a data line 'replot' is received. This 'replot' command works in both triggered
and timed modes, but in triggered mode, it's the only way to replot.

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 can be inferred from the filename, if B<.ps>, B<.eps>, B<.pdf>,
B<.svg> or B<.png> is requested. If any other file type is requested,
C<--terminal> I<must> be passed in to tell gnuplot how to make the plot.

=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.

=head1 ARGUMENTS

  --[no]domain         If enabled, the first element of each line is the
                       domain variable.  If not, the point index is used

  --[no]dataid         If enabled, each data point is preceded by the ID
                       of the data set that point corresponds to. This ID is
                       interpreted as a string, NOT as just a number. If not
                       enabled, the order of the point is used.

As an example, if line 3 of the input is "0 9 1 20"
 '--nodomain --nodataid' would parse the 4 numbers as points in 4
   different curves at x=3

 '--domain --nodataid' would parse the 4 numbers as points in 3 different
   curves at x=0. Here, 0 is the x-variable and 9,1,20 are the data values

 '--nodomain --dataid' would parse the 4 numbers as points in 2 different
   curves at x=3. Here 0 and 1 are the data IDs and 9 and 20 are the
   data values

 '--domain --dataid' would parse the 4 numbers as a single point at
   x=0. Here 9 is the data ID and 1 is the data value. 20 is an extra
   value, so it is ignored. If another value followed 20, we'd get another
   point in curve ID 20

  --[no]3d             Do [not] plot in 3D. This only makes sense with --domain.
                       Each domain here is an (x,y) tuple

  --colormap           Show a colormapped xy plot. Requires extra data for the color.
                       zmin/zmax can be used to set the extents of the colors.
                       Automatically increments extraValuesPerPoint

  --stream [period]    Plot the data as it comes in, in realtime. If period is given,
                       replot every period seconds. If no period is given, replot at
                       1Hz. If the period is given as 0 or 'trigger', replot ONLY when
                       the incoming data dictates this . See the "Real-time streaming
                       data" section of the man page.

  --[no]lines          Do [not] draw lines to connect consecutive points
  --[no]points         Do [not] draw points
  --circles            Plot with circles. This requires a radius be specified for
                       each point. Automatically increments extraValuesPerPoint

  --xlabel xxx         Set x-axis label
  --ylabel xxx         Set y-axis label
  --y2label xxx        Set y2-axis label. Does not apply to 3d plots
  --zlabel xxx         Set y-axis label. Only applies to 3d plots

  --title  xxx         Set the title of the plot

  --legend curveID legend
                       Set the label for a curve plot. Use this option multiple times
                       for multiple curves. With --dataid, curveID is the ID. Otherwise,
                       it's the index of the curve, starting at 0

  --autolegend         Use the curve IDs for the legend. Titles given with --legend
                       override these

  --xlen xxx           When using --stream, sets the size of the x-window to plot.
                       Omit this or set it to 0 to plot ALL the data. Does not
                       make sense with 3d plots. Implies --monotonic

  --xmin  xxx          Set the range for the x axis. These are ignored in a
                       streaming plot
  --xmax  xxx          Set the range for the x axis. These are ignored in a
                       streaming plot
  --ymin  xxx          Set the range for the y axis.
  --ymax  xxx          Set the range for the y axis.
  --y2min xxx          Set the range for the y2 axis. Does not apply to 3d plots.
  --y2max xxx          Set the range for the y2 axis. Does not apply to 3d plots.
  --zmin  xxx          Set the range for the z axis. Only applies to 3d plots or colormaps.
  --zmax  xxx          Set the range for the z axis. Only applies to 3d plots or colormaps.

  --y2    xxx          Plot the data specified by this curve ID on the y2 axis.
                       Without --dataid, the ID is just an ordered 0-based index.
                       Does not apply to 3d plots. Can be passed multiple times, or passed a
                       comma-separated list

  --histogram  curveID
                       Set up a this specific curve to plot a histogram. The bin
                       width is given with the --binwidth option (assumed 1.0 if
                       omitted). --histogram does NOT touch the drawing style.
                       It is often desired to plot these with boxes, and this
                       MUST be explicitly requested with --curvestyleall 'with
                       boxes'. This works with --domain and/or --stream, but in
                       those cases the x-value is used ONLY to cull old data
                       because of --xlen or --monotonic. I.e. the x-values are
                       NOT drawn in any way. Can be passed multiple times, or passed a comma-
                       separated list
  --binwidth width     The width of bins when making histograms. This setting applies to ALL
                       histograms in the plot. Defaults to 1.0 if not given.
  --histstyle style    Normally, histograms are generated with the 'smooth freq'
                       gnuplot style. --histstyle can be used to select
                       different 'smooth' settings. Allowed are 'unique',
                       'cumulative' and 'cnormal'. 'unique' indicates whether a
                       bin has at least one item in it: instead of counting the
                       items, it'll always report 0 or 1. 'cumulative' is the
                       integral of the "normal" histogram. 'cnormal' is like
                       'cumulative', but rescaled to end up at 1.0.

  --curvestyle curveID style
                       Additional styles per curve. With --dataid, curveID is the
                       ID. Otherwise, it's the index of the curve, starting at 0. Use
                       this option multiple times for multiple curves

  --curvestyleall xxx  Additional styles for ALL curves.

  --extracmds xxx      Additional commands. These could contain extra global styles
                       for instance. Can be passed multiple times, or passed a comma-
                       separated list

  --square             Plot data with aspect ratio 1. For 3D plots, this controls the
                       aspect ratio for all 3 axes

  --square_xy          For 3D plots, set square aspect ratio for ONLY the x,y axes

  --hardcopy xxx       If not streaming, output to a file specified here. Format
                       inferred from filename, unless specified by --terminal
  --terminal xxx       String passed to 'set terminal'. No attempts are made to
                       validate this. --hardcopy sets this to some sensible
                       defaults if --hardcopy is given .png, .pdf, .ps, .eps or
                       .svg. If any other file type is desired, use both
                       --hardcopy and --terminal

  --maxcurves xxx      The maximum allowed number of curves. This is 100 by default,
                       but can be reset with this option. This exists purely to
                       prevent perl from allocating all of the system's memory when
                       reading bogus data

  --monotonic          If --domain is given, checks to make sure that the x-
                       coordinate in the input data is monotonically increasing.
                       If a given x-variable is in the past, all data currently
                       cached for this curve is purged. Without --monotonic, all
                       data is kept. Does not make sense with 3d plots.
                       No --monotonic by default.

  --extraValuesPerPoint xxx
                       How many extra values are given for each data point. Normally this
                       is 0, and does not need to be specified, but sometimes we want
                       extra data, like for colors or point sizes or error bars, etc.
                       feedgnuplot options that require this (colormap, circles)
                       automatically set it. This option is ONLY needed if unknown styles are
                       used, with --curvestyleall for instance

  --dump               Instead of printing to gnuplot, print to STDOUT. For
                       debugging.

  --geometry           If using X11, specifies the size, position of the plot window

=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<< <dima@secretsauce.net> >>

=head1 LICENSE AND COPYRIGHT

Copyright 2011-2012 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