MATLAB: Rotating a line given the angle and a vector

rotation of vector

I have 2 points (x1, y1) and (x2, y2). I want to rotate it clockwise by 123 deg and find the co-ordinate (x2', y2') after rotation. Can anyone help?

Best Answer

p1 = rand(2,1) ;
p2 = rand(2,1) ;
%%rotation matrix 
th = 123*pi/180 ;
R = [cos(th) -sin(th) ;sin(th) cos(th)] ;
%%rotate points
pr2 = R*p2 ;
figure
hold on
plot([p1(1) p2(1)],[p1(2) p2(2)] ,'r') ;
plot([p1(1) pr2(1)],[p1(2) pr2(2)] ,'b') ;

Read about rotation matrix: https://en.wikipedia.org/wiki/Rotation_matrix

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MATLAB: How to calculate a angle between two vectors in 3D

This code uses your angle calculation and shows for different reference points (3d). 2d is the same for your formula.

% Origin is reference point
p1 = 1*ones(1,3); % directly v1 = p1 
p2 = 2*ones(1,3); % directly v2 = p2
% With origin as the reference point, the angle between vectors is 0
ang = rad2deg(atan2(norm(cross(p1,p2)),dot(p1,p2)));
disp(ang)
% Choosing reference point such that new v1, v2 are at 90 degrees
refpoint = [2 2 1];
v1 = p1 - refpoint;
v2 = p2 - refpoint;
angNew = rad2deg(atan2(norm(cross(v1,v2)),dot(v1,v2)));
disp(angNew)

MATLAB: 2d Coordinate rotation in clockwise direction

th = pi/4 ;
R = [cos(th) -sin(th) ;sin(th) cos(th)] ;

Multiply your points with the above R. Read about rotation matrix: https://en.wikipedia.org/wiki/Rotation_matrix

Best Answer

Related Solutions

MATLAB: How to calculate a angle between two vectors in 3D

MATLAB: 2d Coordinate rotation in clockwise direction

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