On Thu, Mar 12, 2009 at 6:05 PM, Sébastien Morin <sebastien.mori...@ulaval.ca> wrote: > Hi, > > In an attempt to find the problem causing this bug, I dug into the code > and found something which could be erroneous... This alone does not fix > the bug, but may be part of the fix (or not)... > > In function math_fns/direction_cosine.calc_ellipsoid_di(), there could > be an error at line 229: > > diff_data.dz[1] = data.sin_b * data.sin_g > > If I am right (?), this part of the code is related to page 193 of > Edward d'Auvergne's thesis: > > c11 = diff_data.dx[0] > c21 = diff_data.dx[1] > c31 = diff_data.dx[2] > > c12 = diff_data.dy[0] > c22 = diff_data.dy[1] > c32 = diff_data.dy[2] > > c13 = diff_data.dz[0] > c23 = diff_data.dz[1] --> FALSE !!!! > c33 = diff_data.dz[2] > > Indeed, > c23 = sin(beta) * cos(gamma), > whereas > diff_data.dz[1] = data.sin_b * data.sin_g > > > Thus, either me, the code or Edward's thesis are erroneous here... > > Am I right ?
These unit vectors are the columns of the reverse matrix, or the transpose, or simply rows of the normal matrix. This depends if you are defining the rotation from being from the diffusion tensor frame to the lab frame or the reverse - both are related by the transpose. Hence this value is c32 which in my thesis is sin(alpha)*sin(beta). Does this answer your question and solve the issue? There could be bugs elsewhere in here though because of this. Regards, Edward _______________________________________________ relax (http://nmr-relax.com) This is the relax-users mailing list relax-users@gna.org To unsubscribe from this list, get a password reminder, or change your subscription options, visit the list information page at https://mail.gna.org/listinfo/relax-users
