How to rotate points on 2D coordinate systems

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Rightia Rollmann
Rightia Rollmann 2017-2-5
评论： George Abrahams 2024-2-12
I have some points on a 2D Cartesian coordinate system. I want to rotate all these points 90 degrees counterclockwise. What is the best solution? (When I work with 3D coordinates, I use “view” to change the view direction, but apparently, it doesn’t work with 2D coordinates)

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John Chilleri
John Chilleri 2017-2-6
Hello,
You can rotate your points with a rotation matrix:
Here's a simple implementation,
% Create rotation matrix
theta = 90; % to rotate 90 counterclockwise
R = [cosd(theta) -sind(theta); sind(theta) cosd(theta)];
% Rotate your point(s)
point = [3 5]'; % arbitrarily selected
rotpoint = R*point;
The rotpoint is the 90 degree counterclockwise rotated version of your original point.
Hope this helps!
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Ria
Ria 2024-2-12
Hello, if you needed the rotation clockwise, could you just reverse each sign of cosd and sind?
George Abrahams
George Abrahams 2024-2-12
Ran in:
@Ria You have two options. First option, set theta, the angle of rotation, to -90. Second option, the inverse of a rotation matrix is its transpose, , so transpose the matrix. In MATLAB this is typically achieved with the .' syntax.
R = [cosd(-90) -sind(-90); sind(-90) cosd(-90)]
R = 2×2
0 1 -1 0
R = [cosd(90) -sind(90); sind(90) cosd(90)].'
R = 2×2
0 1 -1 0

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Amit
Amit 2023-3-29
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Amit
Amit 2023-3-29
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