Maria: You can use the 'EdgeColor' property of rectangle() to draw circles in different colors. You can use the built-in colormap palettes, like jet() or hsv() or hot() or whatever, to create a list of colors. See this code:
numRadii = 20;
colors = jet(numRadii);
xCenter = 50;
yCenter = 60;
for r = 1 : numRadii
leftTopWidthHeight = [xCenter-r/2, yCenter-r/2, r, r];
rectangle('Position', leftTopWidthHeight,...
'Curvature', [1 1], ...
'LineWidth', 4, ...
'EdgeColor', colors(r, :))
hold on;
axis equal
end
grid on;
% Set up figure properties:
% Enlarge figure to full screen.
set(gcf, 'Units', 'Normalized', 'OuterPosition', [0 0 1 1]);
% Get rid of tool bar and pulldown menus that are along top of figure.
set(gcf, 'Toolbar', 'none', 'Menu', 'none');
% Give a name to the title bar.
set(gcf, 'Name', 'Demo by ImageAnalyst', 'NumberTitle', 'Off')
