MATLAB: Why cant i rotate the 2nd line at the X axis it takes reference as point 0,0 and rotates at 45 degree angle i want to rotate the line at same axis

rotate

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It is rotating. Look at the top of your plot.

The way to rotate relative to a point is to subtract the coordinates of the point to rotate around, do the rotation, then add the coordinates of the point to rotate around back in. If you want ot rotate around (800,0) then cart2pol(x1-800,y1) and plot(x1r+800,y1r)

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MATLAB: How to rotate a line

This should answer your question. This code does what you want and shows you what happens depending on your choice of centre point of rotation. (Look up rotation matrices and direction cosine matrices for more information). This is an example for 3D rotation for 2D in the plane you could simplify and only use the Rz part.

Kevin

clear all; close all; clc;
%Example coordinates
y=[2 4 6 8 10];
x=ones(size(y));
%Vertices matrix
V=[x(:) y(:) zeros(size(y(:)))];
V_centre=mean(V,1); %Centre, of line
Vc=V-ones(size(V,1),1)*V_centre; %Centering coordinates
a=30; %Angle in degrees
a_rad=((a*pi)./180); %Angle in radians
E=[0  0 a_rad]; %Euler angles for X,Y,Z-axis rotations
%Direction Cosines (rotation matrix) construction
Rx=[1        0        0;...
    0        cos(E(1))  -sin(E(1));...
    0        sin(E(1))  cos(E(1))]; %X-Axis rotation
Ry=[cos(E(2))  0        sin(E(2));...
    0        1        0;...
    -sin(E(2)) 0        cos(E(2))]; %Y-axis rotation
Rz=[cos(E(3))  -sin(E(3)) 0;...
    sin(E(3))  cos(E(3))  0;...
    0        0        1]; %Z-axis rotation
R=Rx*Ry*Rz; %Rotation matrix
Vrc=[R*Vc']'; %Rotating centred coordinates
Vruc=[R*V']'; %Rotating un-centred coordinates
Vr=Vrc+ones(size(V,1),1)*V_centre; %Shifting back to original location
figure;
plot3(V(:,1),V(:,2),V(:,3),'k.-','MarkerSize',25);  hold on; %Original
plot3(Vr(:,1),Vr(:,2),Vr(:,3),'r.-','MarkerSize',25); %Rotated around centre of line
plot3(Vruc(:,1),Vruc(:,2),Vruc(:,3),'b.-','MarkerSize',25); %Rotated around origin
axis equal; view(3); axis tight; grid on;

MATLAB: What is the rotation sequence for the Euler angles in the Quaternions to Euler Angles block in the Aerospace Blockset

Documentation on the Quaternions to Euler Angles block (for the default sequence of rotation for the Euler angles) is missing from the Aerospace Blockset manual.

Here is additional information on the Quaternions to Euler Angles block:

The sequence of rotation for the Euler angles is 3-2-1. The angles are output as Roll, Pitch, Yaw (X, Y, Z).

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MATLAB: How to rotate a line

MATLAB: What is the rotation sequence for the Euler angles in the Quaternions to Euler Angles block in the Aerospace Blockset

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