On Thu, Mar 12, 2009 at 7:04 PM, Sébastien Morin <sebastien.mori...@ulaval.ca> wrote: > Edward d'Auvergne wrote: >> 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. >> >> > Ok... I am far from an expert in trigonometry... :p > > If I understand well what you wrote, there is no error in the code or > the thesis ? Or should something be corrected ?
Sorry, I had a much closer look and you are correct - there is an error there. The problem is a typo in equation 6.61 (page 193) of my thesis, c23 should be sin(beta) * sin(gamma). I double checked using wikipedia and tracked it back to the thesis. Glad that it's in the thesis and not the code!!! Cheers, Edward P.S. It would be useful if you could confirm that the problem is indeed in the thesis and not the code ;) _______________________________________________ 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
