NAME

   Graphics::Skullplot - Plot the result of an SQL select (e.g. from an
   emacs shell window)

VERSION

   Version 0.01

SYNOPSIS

      # To use this from emacs, see scripts/skullplot.el.
      # That elisp code accesses the perl script: scripts/skullplot.pl

      # the code used by skullplot.pl
      my $plot_hints = { indie_count           => $indie_count,
                         dependent_requested   => $dependent_requested,
                         independent_requested => $independent_requested,
                       };
      my %gsp_args =
        ( input_file   => $dbox_file,
          plot_hints   => $plot_hints, );
      $gsp_args{ working_area } = $working_area if $working_area;
      $gsp_args{ image_viewer } = $image_viewer if $image_viewer;
      my $gsp = Graphics::Skullplot->new( %gsp_args );

      $gsp->show_plot_and_exit();  # does an exec

DESCRIPTION

   Graphics::Skullplot is a module that works with the result from a
   database select in the common tabular text "data box" format. It has
   routines to generate and display plots of the data in png format.

   Internally it uses the Table::BoxFormat module to parse the text table,
   and the Graphics::Skullplot::ClassifyColumns module to determine the
   types of the columns.

   The default image viewer is the ImageMagick "display" command.

   The immediate use for this code is to act as the back-end for the
   included Emacs package scripts/skullplot.el, so that database select
   results generated in an emacs shell window can be immediately plotted.

   This elisp code calls scripts/skullplot.pl, which might be used in
   other contexts.

METHODS

   new

     Creates a new Graphics::Skullplot object. Object attributes:

     working_area

       Scratch location where intermediate files are created. Defaults to
       "/tmp".

     image_viewer

       Defaults to 'display', the ImageMagick viewer (a dependency on
       Image::Magick ensures it's available)

   builder methods (largely for internal use)

     builder_image_viewer Currently just returns a hardcoded selection
     (the ImageMagick "display" program).

   generate_output_filenames

     Example usage:

       # relies on object settings: "input_file" and "working area"
       my $fn =
         generate_filenames();
       my $basename = $fn->{ base };
       # full paths to file in $working_area
       my $tsv_file  = $fn->{ tsv };
       my $png_file  = $fn->{ png };

   plot_tsv_to_png

     Generate the r-code to plot the tsv file data as the png file. Takes
     one argument, a hash of "field metadata".

     The file names (tsv, png, plus internal formats) come from the
     "naming" object field.

     Example usages:

       $self->plot_tsv_to_png( $plot_cols );

   generate_png_file

     Example usage:

       $self->generate_png_file( $pc, $fn );

     Runs the given plot code (first argument) using the file-name
     metadata (second argument, defaults to object's naming), saving the
     plot as a png file ($fn->{png}).

     This generates a file of R code to run with an Rscript call. In debug
     mode, this generates a standalone unix script. ($DEBUG).

   display_png_and_exit

     Open the given png file in an image viewer Defaults to "png" field in
     object's "naming".

     This internally does an exec: it should be the last thing called.

     The image viewer can be set as the second, optional field. The
     default image viewer is ImageMagick's "display".

     Example usage:

       my $naming = $self->naming;
       my $png_file = $naming->{ png };
       $self->display_png_and_exit( $png_file );

   show_plot_and_exit

     The method called by the skullplot.pl script to actually plot the
     data from a "data box format" file, using the plot_hints.

     It's expected that the dbox file (input_file) and the plot_hints will
     be defined at object creation, but at present those settings may be
     overridden here and given as first and second arguments.

     This should be used at the end of the program (internally it does an
     "exec").

   classify_columns

     Given a reference to the tabular data in the form of an array of
     arrays, returns metadata for each column to be used in deciding how
     to plot the data.

     Example usage:

       my $plot_cols = $self->classify_columns( $data );

     Classify the columns from the tabular data, returning a
     "fields_metadata" hash ref.

     This is a wrapper around a provisional technique to make it easier to
     swap in better ones later.

     At present, the metadata fields are:

          x           => $x_field  (( rename indie_x ))
          y           => $y_field
          gb_cats      => [ @gb_cats ]
          dependents_y => [ @dependents_y ]

   dumporama

     Report on state of object fields.

   fryhash

NOTES

TODO

     * Limited to two group by categories (in addition to the x-axis):
     used with colour & shape If there's more than 2, fuse them together
     into a compound, use with colour

     * See R Graphics Cookbook, p.205: setting up the tics and labels.

         $pc .= 'p + scale_x_date';
         $pc .= '';

     * Currently this defaults to viewing images using the "display"
     program. Alternately, the builder_image_viewer could scan through a
     list of likely viewers and pick the first that's installed.

AUTHOR

   Joseph Brenner, <[email protected]>, 16 Nov 2016

COPYRIGHT AND LICENSE

   Copyright (C) 2016 by Joseph Brenner

   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.

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