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=cut

sub _scaley {
  my $self = shift;
  my $y    = shift; #units
  my $max  = $self->maxy;
  my $min  = $self->miny;
  my $s    = 1;
  if (defined($max) and defined($min) and $max-$min) {
    $s=($max - $min) / ($self->height - 2 * $self->bordery); #units/pixel
  }
  return $y / $s; #pixels
}

=head2 _imgxy_xy

Method to convert xy to imgxy coordinates

=cut

sub _imgxy_xy {
  my $self = shift;
  my $x    = shift;
  my $y    = shift;
  return ($self->_imgx_x($x), $self->_imgy_y($y));
}

sub _imgx_x {
  my $self = shift;
  my $x    = shift;
  return $self->borderx + $self->_scalex($x - $self->minx);
}

sub _imgy_y {
  my $self = shift;
  my $y    = shift;
  return $self->height - ($self->bordery + $self->_scaley($y - $self->miny));
}

=head1 TODO

I'd like to add this capability into L<Chart> as a use base qw{Chart::Base}

=head1 BUGS

Log on RT and email the author

=head1 LIMITS

There are many packages on CPAN that create graphs and plots from data.  But, each one has it's own limitations.  This is the research that I did so that hopefully you won't have to...

=head2 Similar CPAN Packages

=head3 L<Chart::Plot>

This is the second best package that I could find on CPAN that supports scatter plots of X/Y data.  However, it does not supports a zero based Y-axis for positive data.  Otherwise this is a great package.

=head3 L<Chart>

This is a great package for its support of legends, layouts and labels but it only support equally spaced x axis data.

=head3 L<GD::Graph>

This is a great package for pie charts but for X/Y scatter plots it only supports equally spaced x axis data.

=head1 AUTHOR

Michael R. Davis qw/perl michaelrdavis com/

=head1 LICENSE

Copyright (c) 2009 Michael R. Davis (mrdvt92)

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

=head1 SEE ALSO

L<GD::Graph::Cartesian>, L<GD>, L<Chart::Plot>, L<Chart>, L<GD::Graph>

=cut

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