How can i divide a circle into 12 parts? 6 sectors having 15 degrees and the rest 6 having 30 degrees?

How can i divide a circle into 12 parts? 6 sectors having 15 degrees and the rest 6 having 45 degrees? How do i mask each 30 degree sector?

Answer 1

[Azzi Abdelmalek]

t=-pi:0.01:pi;
r=1;
x=cos(t);
y=sin(t);
plot(x,y)
axis square
hold on
t1=linspace(-pi/2,pi/2,7)
x1=cos(t1);
y1=sin(t1);
x2=zeros(size(x1))
y2=zeros(size(x1))
plot([x1;x2],[y1;y2])
t1=linspace(pi/2,3*pi/2,13)
x1=cos(t1);
y1=sin(t1);
x2=zeros(size(x1))
y2=zeros(size(x1))
plot([x1;x2],[y1;y2])

[MoonPie1]

Actually i am working on an image..How can i mask each sector and get only one sector as '1' and the rest as 0?

[Image Analyst]

You haven't explained your needs well. However you've accepted an answer so is this working or not? If not, then post your image so we can see what you're talking about, and try to figure out why you're not able to use poly2mask to mask out the sectors you needs. Also, attach any existing code you have http://www.mathworks.com/matlabcentral/answers/6200-tutorial-how-to-ask-a-question-on-answers-and-get-a-fast-answer

[John D'Errico]

I'm just wondering how you are able to dive a circle, which is made of 360 degrees, into 6 parts of 15, and 6 parts of 30. Hmm

6*15 + 6*30 = 270

Falls short by 90.

[Image Analyst]

She wanted six 45 degree sectors. The confusing part comes in the next sentence where she then refers to 12 30 degree sectors after she just said that there were supposed to be sectors of only 15 and 45 degrees. That's why I asked for the image.

[MoonPie1]

My needs are as follows:

1. I want to divide the image into 6 sectors named 1 to 6.
2. I want to obtain a mask of each sectors such that only one sector is visible.
3. After masking I want to multiply the mask with the original image.

Answer 2

[Image Analyst]

So I guess the problem is not solved yet. So, you should look at the FAQ http://matlab.wikia.com/wiki/FAQ#How_do_I_create_an_arc.3F and then once you have the coordinates of the sector, use the poly2mask() function to make your mask. Not hard. Let me know if you have problems.