plotting circles

Asked by Yasmine Tamimi on 12 Mar 2011

Latest activity Edited by Image Analyst on 20 Aug 2018

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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.

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Answer by Paulo Silva on 12 Mar 2011

Accepted Answer

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.

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Bud Kelly on 2 Apr 2018

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! ;-)

faiza gul on 20 Aug 2018

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 on 20 Aug 2018

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

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Answer by Michelle Hirsch on 29 Jan 2016

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

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Image Analyst on 29 Jan 2016

And with R2012a and later you can use viscircles

Ronald Mintz on 14 Apr 2016

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

Image Analyst on 14 Apr 2016

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.

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Answer by Image Analyst on 5 Jul 2012

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

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Answer by Chad Greene on 21 Aug 2014

This'll do the job.

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Answer by Image Analyst on 20 Jan 2016

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

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