function double_plot ( prefix )

%*****************************************************************************80
%
%% double_plot() makes a doubled plot of points from a data file.
%
%  Licensing:
%
%    This code is distributed under the MIT license.
%
%  Modified:
%
%    22 November 2020
%
%  Author:
%
%    John Burkardt
%
%  Input:
%
%    character string PREFIX.
%
  file_text = sprintf ( '%s.txt', prefix );

  xy = load ( file_text );
%
%  We are assuming that the original data X values lie in 0 <= X <= 1.
%
  clf ( );
  hold ( 'on' );
  plot ( xy(1,:),       xy(2,:), 'b.', 'MarkerSize', 20 );
  plot ( xy(1,:) + 1.0, xy(2,:), 'b.', 'MarkerSize', 20 );
  hold ( 'off' );
%
%  Use the same scale on both axes.
% 
  axis equal
%
%  Make the axes just fit the data.
%
  axis tight
%
%  Don't show the axis tick marks and lines.
%
  axis off
%
%  Save the graphics data as a PNG.
%
  file_png = sprintf ( '%s_double.png', prefix );

  print ( '-dpng', file_png );

  return
end

