plotting circles

How can I plot circles, same radius and different centers, all in one graph. I used the following command to draw +,o,diamond: plot (x,y,'ro',u,v,'gd',A,B,'b+'); where x,y,u,v,A,B are all row vectors. And I want to add circles to that plot where the o will be the center.

[fatima ibrahim]

function draw_circle1(x,y,R,c)

t =0:0.05:6.28;

x1 = (x +R*cos(t))';

y1= (x +R*sin(t))';

Answer 1

[Paulo Silva]

Here's a function to draw circles:

function circle(x,y,r)
%x and y are the coordinates of the center of the circle
%r is the radius of the circle
%0.01 is the angle step, bigger values will draw the circle faster but
%you might notice imperfections (not very smooth)
ang=0:0.01:2*pi; 
xp=r*cos(ang);
yp=r*sin(ang);
plot(x+xp,y+yp);
end

If you want to add circles you must insert the command

hold on

before the circles being added.

[Firas]

That's awesome

[Eddie]

Thanks a lot, this is great. If I had some time, I would probably tweak your code and try to plot open intervals on the real line, that's what I really need, but circles are fine too.

[Bud Kelly]

There are coding solutions and there are coding solutions. The ones that accomplish the task as this one does are...elegant... beautiful... art. Thank you, you may consider it stolen! ;-)

[passioncoding]

I have been trying to create function for circle with function that mentioned above ,but I am getting this "Not enough input arguments" for "xp=r*cos(ang)". kindly help me in this regard

[Image Analyst]

What is ang for you? Did you comment out or delete the line

ang=0:0.01:2*pi;

??? You did one or the other because if you didn't, ang would exist and you would not get that error.

Do you know how to debug by setting a breakpoint on that line and looking at its value? If not, see this link

[Özgür Saglam]

what does 0.01 in ang mean? i dont understand this part

[Rik]

It's the step size. You can use the colon in two ways when you create an array:

start:stop
start:step:stop

[Özgür Saglam]

Thank you very much!

Answer 2

[Michelle Hirsch]

It's counter-intuitive, but this is actually really easy with the rectangle function. From the rectangle documentation :

   pos = [2 4 2 2];
   rectangle('Position',pos,'Curvature',[1 1])
   axis equal

[Image Analyst]

And with R2012a and later you can use viscircles

numCircles = 15;
x = 5 + randi(95, numCircles, 1);
y = 5 + randi(95, numCircles, 1);
radius = 2 * ones(numCircles, 1);
viscircles([x, y], radius);
grid on;
axis equal

[Ronald Mintz]

Thanks very much Michelle. Your idea made beautiful concentric circles. viscircles didn't work on my computer because I have version R2011a.

[Image Analyst]

rectangle() is one of several methods listed in the FAQ: http://matlab.wikia.com/wiki/FAQ#How_do_I_create_a_circle.3F> You'll have lots of other nice improvements that they've made over the last 5 years if you upgrade.

numCircles = 15;
x = 5 + randi(95, numCircles, 1);
y = 5 + randi(95, numCircles, 1);
radius = 2 * ones(numCircles, 1);
viscircles([x, y], radius);
grid on;
axis equal

[Royi Avital]

@Michelle Hirsch, It would be great if it had the DisplayName property like most other objects.

It makes easier when adding it to the legend.

[Michelle Hirsch]

@Royi Avital I think it's more than just adding DisplayName - annotations like rectangle (intentionally) don't show up in legend since they are meant to be annotations, not data. Are you interested in being able to include annotations in legend? If so, please share more about your use case so I make sure we understand what you are thinking.

Answer 3

[Chad Greene]

This'll do the job.

Answer 4

[Image Analyst]

There is now a function called viscircles(): http://www.mathworks.com/help/images/ref/viscircles.html?s_tid=srchtitle

numCircles = 15;
x = 5 + randi(95, numCircles, 1);
y = 5 + randi(95, numCircles, 1);
radius = 2 * ones(numCircles, 1);
viscircles([x, y], radius);
grid on;
axis equal

Or, please refer to the FAQ: http://matlab.wikia.com/wiki/FAQ#How_do_I_create_a_circle.3F