# what's the code inside angle2dcm?

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yunya liu on 27 Apr 2022
Commented: yunya liu on 28 Apr 2022
I saw angle2dcm on Mathworks but don't know how scalars of x,y,z or vectors of x,y,z become matrix after using angle2dcm.
Can anyone explain the code embedded?
Thanks very much.

Mathieu NOE on 27 Apr 2022
hello
here you are
notice that there are some issues / questions about orientation convention with this function
function [dcm] = angle2dcm(r,seq)
% dcm = angle2dcm(r1,r2,r3,seq)
% builds euler angle rotation matrix
%
% r = [r1 r2 r3]
% seq = 'ZYX' (default)
% 'ZXZ'
% dcm = direction cosine matrix
if nargin == 1
seq = 'ZYX';
end
switch seq
case 'ZYX'
dcm = Tx(r(3))*Ty(r(2))*Tz(r(1));
case 'ZXZ'
dcm = Tz(r(3))*Tx(r(2))*Tz(r(1));
end
function A = Tx(a)
A = [1 0 0;0 cosd(a) sind(a);0 -sind(a) cosd(a)];
function A = Ty(a)
A = [cosd(a) 0 -sind(a);0 1 0;sind(a) 0 cosd(a)];
function A = Tz(a)
A = [cosd(a) sind(a) 0;-sind(a) cosd(a) 0;0 0 1];
yunya liu on 28 Apr 2022
Very detailed description. Thanks so much.

Jan on 27 Apr 2022
While I cannot find the code of angle2dcm , the equivalent function eul2rotm is useful for the explanation also. It produces the transposed matrix compared to angle2dcm.
See:
edit eul2rotm
3 angles define the attitude of a coordinate system. The "dcm" matrix (direction cosine matrix) contains the 3 unit vectors of the base of a rotated coordinate system.
yunya liu on 28 Apr 2022
Thank you