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MathGroup Archive 1993

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Rotations.m package bug?

  • To: mathgroup at yoda.physics.unc.edu
  • Subject: Rotations.m package bug?
  • From: bestor at cs.wisc.edu (Gareth Bestor)
  • Date: Fri, 17 Dec 93 14:55:22 -0600

I think something is wrong here:

Chop[RotationMatrix3D[00 Degree, 0 Degree, 0 Degree] //N]
{{1., 0, 0}, {0, 1., 0}, {0, 0, 1.}}

Chop[RotationMatrix3D[90 Degree, 0 Degree, 0 Degree] //N]
{{0, 1., 0}, {-1., 0, 0}, {0, 0, 1.}}

Chop[RotationMatrix3D[0 Degree, 90 Degree, 0 Degree] //N]
{{1., 0, 0}, {0, 0, 1.}, {0, -1., 0}}

Chop[RotationMatrix3D[0 Degree, 0 Degree, 90 Degree] //N]
{{0, 1., 0}, {-1., 0, 0}, {0, 0, 1.}}

Note that the 2nd and 3rd above are the same. The package uses
Euler angles to specify the rotation (I'm not certain how
the axes are aligned, but it doesn't really matter). It appears
to be impossible to get rotation around each of the 3 principle
axes.

Am I making a mistake or is something wrong with RotationMatrix3D?

Also, there's a discrepency between the order of the Euler angles
in the definition of RoatationMatrix3D and where its called in
Rotate3D in the same package (phi,theta,psi  vs  theta,pha,psi).

I'm running M2.0 (but the package in 2.1 is the same I think;
don't have access to 2.2).

- Gareth





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