MATLAB: How to plot left semi_circle in matlab? (Given, x(origin), y(origin) and r(radius) of the circle)

circle shapesfaqhalf circlesemi circle

I was just wandering how to plot left semi circle. given x,y and radius of the circle.

For example, x=5, y=10, r=3

Best Answer

How to plot left semi circle:

The key is to compute theta values between pi/2 and 3*pi/2.

x=5;      
y=10;
r=3;
theta = linspace(pi/2, 3*pi/2, 100);  % <-- left half of circle
xCirc = r * cos(theta) + x;
yCirc = r * sin(theta) + y;
cla()
plot(xCirc, yCirc)
axis equal
grid on
xline(x)
yline(y)

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MATLAB: Circle packed with Circles

Here the code :

First, you need to create a m-file

function [X Y] = circle(center,radius,n)
THETA = linspace(0, 2 * pi, n);
RHO = ones(1, n) * radius;
[X Y] = pol2cart(THETA, RHO);
X = X + center(1);
Y = Y + center(2);

Save this code with filename 'circle.m'

Then create a new m-file

function circles(R);
axis([0 2*R 0 2*R]); axis off; grid off; hold on;
[xoc yoc] = circle([R R], R, 1000); % outer circle
plot(xoc, yoc, '-','linewidth',2,'color',0.5.*rand(1,3));
[xcc ycc] = circle([R R], 1, 1000); % center circle
plot(xcc, ycc, '-','linewidth',2,'color',0.5.*rand(1,3));
numlapis = ((2*R) - (R+1)) / 2;
for cnt1 = 1 : numlapis
    lapis(cnt1) = cnt1 * 6;
    [xcoor ycoor] = circle([R R], cnt1*2, lapis(cnt1)+1);
    for cnt2 = 1 : lapis(cnt1)
        [xc yc] = circle([xcoor(cnt2)  ycoor(cnt2)], 1, 1000);       
        plot(xc, yc, '-','linewidth',2,'color',0.5.*rand(1,3));
    end
end

Save this code with filename 'circles.m'

And about how to use it.

After you save the files, you can call it from command window.

Just type 'circles(any diameter)'

Eq : circles(5);

Note that this function works well with odd number.

Just try :)

MATLAB: Shifting origin

I actually did this finally. I scan the image left-to-right and top-to-bottom and stop the moment I find a different pixel than the background. Since I am using im2bw(); the background is white and the character pixel are black.

The moment I find the first black pixel, I store the pixel co-ordinates in 2 variables fr and fc. I then use these variables for further computation (i.e. constructing the grid)

Best Answer

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MATLAB: Circle packed with Circles

MATLAB: Shifting origin

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