Hi Mark,
Thanks for the prompt feedback! As I understand, the rmsdiff measure
is invariant to the order of transform matrices just as |X1 - X2|^2 is
symmetric to both variables?
Thanks!
Leo
On Tue, Jan 31, 2012 at 2:44 PM, Mark Jenkinson <[log in to unmask]> wrote:
> Dear Leo,
>
> There is no right answer.
> The two different ways just average over a slightly different
> spherical ROIs. However, the difference will be pretty minor
> and I can't think of an example where these small differences
> would matter.
>
> All the best,
> Mark
>
>
>
> On 31 Jan 2012, at 22:08, Yiou Li wrote:
>
>> Hi Mark,
>>
>> I want to use rmsdiff to measure the difference between image X1 and
>> X2 in terms of affine linear transformation, to do that, I ran flirt
>> to register X1 to X2, taking X2 as reference image and get the
>> transformation xmat_1_to_2, now I got two slightly different number by
>> running:
>>
>> 1. rmsdiff xmat_identity xmat_1_to_2 X2
>> 2. rmsdiff xmat_1_to_2 xmat_identity X2
>>
>> Can you please advise which one is the correct order in this case?
>>
>> Thanks in advance!
>> Leo
>>
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