Plot an Arc on a 2D Grid by given radius and end points

I have one question, how do I plot the arc on a graph by giving the radius and it end points? It start points is the points set by me take example (2,2). I need draw an arc with radius 3 and end point (5,5) How to write the code for this

Answer 1

[Roger Stafford]

(Correction made)

Point vectors A and B must be column vectors

   A = randn(2,1); % Point A to be on circle circumference
   B = randn(2,1); % Same with point B
   d = norm(B-A);
   R = d/2+rand; % Choose R radius >= d/2
   C = (B+A)/2+sqrt(R^2-d^2/4)/d*[0,-1;1,0]*(B-A); % Center of circle
   a = atan2(A(2)-C(2),A(1)-C(1));
   b = atan2(B(2)-C(2),B(1)-C(1));
   b = mod(b-a,2*pi)+a; % Ensure that arc moves counterclockwise
   t = linspace(a,b,1000);
   x = C(1)+R*cos(t);
   y = C(2)+R*sin(t);
   plot(x,y,'y-',C(1),C(2),'w*')
   axis equal

Note that another possible center can be obtained by

   C2 = (B+A)/2-sqrt(R^2-d^2/4)/d*[0,-1;1,0]*(B-A);

Note 2: If C is chosen, the arc will be <= pi. If C2 is used, arc will be >= pi

[TS Low]

[Roger Stafford]

@TS Low: I was having difficulties with my single quote character. I have presumably corrected that now, as well as added a correction to the 'b' computation.

[TS Low]

What is the c2 use for?

So, the only things that prompt user to do is only A and B?

And what is the meaning of A and B?

[Roger Stafford]

For two given points, A and B, to lie on a circular arc with a given radius, there are two possible centers that can be used. One, in this case C, places the center to the left as you face from A toward B. The other, in this case C2, places the center to the right as you face from A toward B. The way this code is written, the arc always starts at point A with angle a and goes counterclockwise as t increases until reaching point B with angle b, which is always greater than or equal to a. That means if you use center C, you will always get an arc of less than or equal to pi radians. If you use center C2, you will always get an arc of greater than or equal to pi radians.

The user needs to be prompted for three things: point A, point B, and radius R. In this code A and B are each required to be a two-element column vector, that is, a vector with two rows and one column. The first element is to be the x-coordinate and the second the y-coordinate of a point on the circular arc that is to be created. The radius, R, is of course a scalar.

[TS Low]

Where is the point A? in term of X1 and Y1

A = randn(2,1);?

And how about radius?

I didn use your solution because i replace the value with other but cant solve.

Answer 2

[KSSV]

https://in.mathworks.com/matlabcentral/answers/327895-how-do-i-plot-a-circular-arc-with-given-two-endpoints-and-radius

Answer 3

[Image Analyst]

See the FAQ: http://matlab.wikia.com/wiki/FAQ#How_do_I_create_an_arc.3F

[TS Low]

yes, it is an arc

by i need prompt user for start point end point and radius

so this might be no work for me

Answer 4

[Ade Ade]

%Equation of a circle with centre (a,b) is (x-a)^2+ (y-b)^2 = r^2

%Circle Centre (1,1), radius = 10

k=1; %counter

c =1 ; % value of x at the centre of the circle

while c <=11

x(k) = c ;

vv = (c-1)^2 ;

y (k) = 1 + real (sqrt (100 - vv) );

c= c + 0.02;

k=k+1;

end

plot (x, y, 'r')

axis equal

Answer 5

[Navinda Wickramasinghe]

The solution was perfect. As Roger mentions, just make sure to provide the endpoint coordinates in the counterclockwise direction.