[MINC-users] xfmavg and lsq6 transforms

[Gabriel A. Devenyi]

This is good to know, CCing in pydpiper guys as this may impact them.

Vlad, would you be willing to share your alternate implementation script?

-- 
Gabriel A. Devenyi B.Eng. Ph.D.
Research Computing Associate
Computational Brain Anatomy Laboratory
Cerebral Imaging Center
Douglas Mental Health University Institute
McGill University
t: 514.761.6131x4781
e: gdevenyi at gmail.com

On Thu, Feb 11, 2016 at 11:55 AM, Vladimir S. FONOV <
vladimir.fonov at gmail.com> wrote:

> So, looks like something is broken in octave, or the way how xfmavg reads
> matrices.
>
> I run standard xfmavg and got result
> -center         0.00000    0.00000    0.00000
> -translation    0.38288    0.50712    0.52295
> -rotation      -0.04862    0.66666   -0.63100
> -scale          1.00000    1.00000    1.00000
> -shear         -0.00000   -0.00000    0.00000
>
> And then run my SciPy based re-implimentation and got following:
> -center         0.00000    0.00000    0.00000
> -translation    0.37409    0.75399    0.28905
> -rotation     -86.85079    2.70359    1.51978
> -scale          1.00000    1.00000    1.00000
> -shear          0.00000    0.00000    0.00000
>
>
>
> The algorithm is the same as in xfmavg - apply matrix logarithm to all
> transforms, perform element-wise averaging, then apply matrix exponent.
>
>
>
> On 16-02-11 11:41 AM, Gabriel A. Devenyi wrote:
>
>> And the average I get, cause I forgot to include it:
>>
>> MNI Transform File
>> %
>> % Created by xfmavg with a bit of help from octave
>> %    http://www.octave.org/
>> %
>> % Thu Feb 11 10:47:59 EST 2016>>>> xfmavg scan1_01a0_GenericAffine.xfm
>> scan1_02a0_GenericAffine.xfm scan1_02b0_GenericAffine.xfm
>> scan1_03a0_GenericAffine.xfm scan1_04a0_GenericAffine.xfm
>> scan1_05a0_GenericAffine.xfm scan1_05b0_GenericAffine.xfm
>> scan1_06a0_GenericAffine.xfm scan1_07a0_GenericAffine.xfm
>> scan1_07b0_GenericAffine.xfm scan1_08b0_GenericAffine.xfm
>> scan1_10b0_GenericAffine.xfm scan1_11b0_GenericAffine.xfm
>> scan1_12a0_GenericAffine.xfm scan1_13a0_GenericAffine.xfm
>> scan1_14a0_GenericAffine.xfm scan1_14b0_GenericAffine.xfm
>> scan1_16b0_GenericAffine.xfm scan2_01a0_GenericAffine.xfm
>> scan2_01b0_GenericAffine.xfm scan2_02a0_GenericAffine.xfm
>> scan2_03a0_GenericAffine.xfm scan2_06a0_GenericAffine.xfm
>> scan2_06b0_GenericAffine.xfm scan2_08a0_GenericAffine.xfm
>> scan2_09a0_GenericAffine.xfm scan2_11a0_GenericAffine.xfm
>> scan3_02a0_GenericAffine.xfm scan3_03a0_GenericAffine.xfm
>> scan3_07a0_GenericAffine.xfm scan3_09a0_GenericAffine.xfm
>> scan3_09b0_GenericAffine.xfm average/average.xfm
>>
>> Transform_Type = Linear;
>> Linear_Transform =
>>   9.99871671e-01 1.10030065e-02 1.16437239e-02 3.82880856e-01
>>   -1.10121374e-02 9.99939105e-01 7.20365393e-04 5.07116829e-01
>>   -1.16350887e-02 -8.48495237e-04 9.99931950e-01 5.22949707e-01;
>>
>> ​
>>
>>
>
> --
> Best regards,
>
>  Vladimir S. FONOV ~ vladimir.fonov <at> gmail.com
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>