Use vrrotvec to calculate the rotation angles between two vectors (R2015b)

I need to calculate the rotation angle to transform vector a = [1, 0, 0]' to b = [1/sqrt(3), 1/sqrt(3), 1/sqrt(3)]',such that I script below:

X = [1, 0, 0]';
Y = [1/sqrt(3), 1/sqrt(3), 1/sqrt(3)]';
R = vrrotvec(X, Y);

As the outcome, I have R = 0, -0.7071, 0.7071, 0.9553

What is the meaning of the first three items, i.e. 0, -0.7071 and 0.7071? Are they the cosine value of the rotation angle against x-, y- and z-axes?

[Image Analyst]

vrrotvec() is not in base MATLAB, nor any of my toolboxes. It's hard to answer your question without seeing the course code of vrrotvec(). You can post it if you want an answer.

[Kerry Schutz]

For ImageAnalyst: vrrotvec is a function included with Simulink 3D Animation, an add-on product. It is not part of base MATLAB.

For Lu Gao: vrrotvec outputs a four element row vector. Per the doc on this function, the first 3 elements specify the rotation axis in 3-D and the last element is the angle of rotation (in radians). For the particular vectors used in your example, the first 3 elements would be computed as: cross(X,Y)/norm(cross(X,Y)) and the 4th element of the row vector is computed as: acos(dot(X,Y))

[Image Analyst]

Thanks, Kerry. I've added it to the list of products below.

[Mritula C]

Wont there 3 rotation angles corresponding to 3 different planes?

[Jan]

Mritula C wrote as flag: "Answer is clear and to the point. thanks"

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Answer 1

[dan]

The first 3 elements is the vector in the first coordinate system. The fourth element is the rotation about the new vector to get to the vector you want.