07-Jan-2022 18:09:38

circles_test():
  MATLAB/Octave version 9.8.0.1380330 (R2020a) Update 2.
  Test CIRCLES.

circles_test01():
  Draw one circle.
  Here we draw one circle of radius 3, centered at (5,10).
  Matlab doesn't set axes equal by default, so circles may not
  look like circles until you declare |axis equal|.

  cla
  circles ( 5, 10, 3 )
  axis equal

  Image saved as "circles_test01.png"

circles_test02():
  Draw 10 circles at x = 1:10, y = 5, of radius 2.
  They will automatically be of varying colors.

  cla
  circles ( 1:10, 5, 2 )
  axis equal

  Image saved as "circles_test02.png"

circles_test03():
  Draw 5 circles at x = 5, y = 15, of radiuses 1:5
  specifying FaceColor None, resulting in hollow or open circles.

  cla
  circles ( 3, 15, 1:5, 'FaceColor', 'None' )
  axis equal

  Image saved as "circles_test03.png"

circles_test04():
  Draw green circles of various locations and sizes.

  x = 22:27;
  y = [5,15,12,25,3,18];
  r = [3 4 5 5 7 3]; 
  cla
  circles ( x, y, r, 'FaceColor', 'Green' )
  axis equal

  Image saved as "circles_test04.png"

circles_test05():
  Draw a circle at x = 5, y = 10, of radius 3.
  Specify the edge color and linewidth.

  cla
  circles ( 5, 10, 3, 'edgecolor', [.5 .2 .9], ...
    'linewidth', 4 )
  axis equal

  Image saved as "circles_test05.png"

circles_test06():
  Draw a grid of circles.

  cla
  lat = repmat ( (10:-1:1)', 1, 10 );
  lon = repmat ( 1:10, 10, 1 );
  r = rand ( size ( lat ) ); 
  circles ( lon, lat, r, 'edgecolor', 'b', ...
    'facecolor', [0.7255 0.6353 0.5059] );
  axis equal

  Image saved as "circles_test06.png"

circles_test07():
  Overlay a parabolic line of semitransparent circles
  on a grid of circles.

  cla
  lat = repmat ( (10:-1:1)', 1, 10 );
  lon = repmat ( 1:10, 10, 1 );
  r = rand ( size ( lat ) ); 
  circles ( lon, lat, r, 'edgecolor', 'b', ...
    'facecolor', [0.7255 0.6353 0.5059] );
  x = 1:.5:10; 
  y = ( x / 4 ) .^ 2;  
  circles ( x, y, .3, 'edgecolor', 'k', ...
    'facecolor', [0.0078 0.5765 0.5255], 'facealpha', .4 );
  axis equal

  Image saved as "circles_test07.png"

circles_test08():
  Circles have corners.
  This script approximates circles as polygons with.
  1000 vertices.  If all those corners are too complex
  for your picture, you can reduce the number of points
  used to make each circle.  Or if 1000 points is not 
  high enough resolution, you can increase the number
  of points.  Or if you'd like to draw triangles or squares
  or pentagons, you can significantly reduce the number of 
  points.  Let's try drawing an 8-sided stop sign:

  cla
  h = circles ( 1, 1, 10, 'vertices', 8, 'color', 'red' ); 
  axis equal

  Image saved as "circles_test08.png"

circles_test09():
  The stop sign in the previous test needs to be rotated.

  cla
  h = circles ( 1, 1, 10, 'vertices', 8, ..
    'color', 'red', 'rot', 45/2 );
  text ( 1, 1, 'STOP', 'fontname','helvetica CY', ...
    'horizontalalignment', 'center', 'fontsize', 120, ...
    'color', 'w', 'fontweight', 'bold' ) 
  axis equal

  Image saved as "circles_test09.png"

circles_test10():
  Rotation can be a scalar or a matrix.
  Plot some squares declaring arbitrary rotation
  corresponding to each square

  cla
  circles ( [1 3 5 7], 2, 1, 'vertices', 4, ...
    'rot', [0 45 35 23.1] );
  axis equal

  Image saved as "circles_test10.png"

circles_test11():
  Draw a grid of circles, use a color map, and color
  each circle according to sqrt(x^2+y^2).

  cla
  c = colormap ( 'jet' );
  [ m, ~ ] = size ( c );
  r = 0.075; 
  r = 0.075; 
  zmin = 0.0; 
  zmax = sqrt ( 8.0 ); 
  hold on; 
  for i = 0 : 8; 
    x = i / 4.0; 
    for j = 0 : 8; 
      y = j / 4.0; 
      z = sqrt ( x * x + y * y );
      indx = fix ( ( m - 1 ) * ( z - zmin ) / ( zmax - zmin ) ) + 1;
      circles ( x, y, r, 'facecolor', c(indx,1:3) );
    end
  end
  axis equal
  hold off

  Image saved as "circles_test11.png"

circles_test():
  Normal end of execution.

07-Jan-2022 18:10:43