function do_plot (term)
  if (nargin < 1)
    term = "wxt";
  endif
  setenv ("GNUTERM", term);

  persistent x y
  if (isempty (x))
    x = 1:4;
    y = rand (4);
  endif

  h = plot (x, y(1,:), "-", ...
            x, y(2,:), "--", ...
            x, y(3,:), "-.", ...
            x, y(4,:), ":");
  set (h, "linewidth", 2);
  drawnow ()

endfunction

## Test script.  use 'source do_plot.m' to test
graphics_toolkit gnuplot

#figure (1)
#do_plot aqua
#keyboard;
figure (2)
do_plot x11
title ("x11");
pause (0.5);
figure (3)
do_plot qt
title ("qt");
pause (0.5);
figure (4)
do_plot wxt
title ("wxt");
pause (0.5);