Best way of drawing multiple circles and updating their position

What is the best way to draw a variable number of circles in a plot and update their position?

I have tried

F = rectangle('Position', [(Xpositions - radius) ...
                (Ypositions - radius) radius*2 radius*2], ...
                'Curvature', [1, 1], 'LineStyle', '--', ...
                'EdgeColor', 'r', 'LineWidth', 3);

but since I have multiple circles I would have to create a for loop to draw each circle.

F = viscircles([Xpositions, Ypositions], ...
                radii, 'LineStyle', '--', 'EdgeColor', 'r', 'LineWidth', 3);

seems to work fine and draw the circles, but it does not provide of a way to update the positions of the circles.

[KALYAN ACHARJYA]

Are you looking for co-centric circles?

[Raldi]

No in fact they have different positions in the plot

Answer 1

[Ameer Hamza]

The easiest is to use rectangle() and use handle F to update the Position property

F.Position = [x y r r]; % specify a new psition
F.Position = [x_ y_ r_ r_]; % specify a new psition

everytime you update Position property, the figure will be updated with the new position.

In older MATLAB version use

set(F, 'Position', [x y r r])

In case of for loop, create an array of handles,

% inside for loop
F(i) = rectangle('Position', [(Xpositions - radius) ...
              (Ypositions - radius) radius*2 radius*2], ...
              'Curvature', [1, 1], 'LineStyle', '--', ...
              'EdgeColor', 'r', 'LineWidth', 3);

and then set the property using F(1), F(2), ... instead of F to change a particular circle.

[Raldi]

Yes I have already tried using rectangle() as stated in my question, but in order to draw multiple circles I would have to make multiple draw calls with a for loop if I am not mistaken.

[Raldi]

So there is no way of skipping the for loop? I will keep doing some tests in case I figure something out and let you know, thanks.

[Ameer Hamza]

Yes, you will need to use for loops. rectangle is a separate graphics object and a call to rectangle() can only create one rectangle. So to draw multiple, a for loop is necessary.

An alternate will be arrayfun, but that is also a fancy way of writing for loop. And in this particular case will not result in any speedup because the actual time-consuming task in your case is the creation of graphics object itself.

Answer 2

[Image Analyst]

The easiest way is to use viscircles() in the Image Processing Toolbox.

Answer 3

[Walter Roberson]

You need a loop or arrayfun() to create multiple rectangle. But once you have those, you can unpdate the positions more compactly.

v = [rectangle('Position', [1 2 1 1]); rectangle('Position', [4 3  2 2])];  %create vector of them somehow
newpos = num2cell(horzcat(v.Position)*2,2);   %calculate new positions
[v.Position] = deal(newpos{:});        %and... action