On 29 May 2012, at 13:52, Ian Tickle wrote:
> In principle there's no reason why you can't invert the hand of the
> indices, as long as the program which does it also takes care to
> convert any hand-dependent columns such as anomalous differences,
> F+/F- etc in the appropriate manner at the same time. The program
> will also need to convert any phase or phase-coefficient columns, but
> it will have to do this anyway, even if the hand is not inverted, in
> those cases where the space group contains screw axes (since then you
> will get phase shifts on reindexing for certain subsets of
> reflections).
>
> So if the data consist only of I's or F's without anomalous data or
> phases then inverting the hand will have absolutely no effect (it's
> called "Friedel's Law").
>
> I note from the documentation that reindex will invert the hand if the
> keyword 'LEFT' is supplied, though whether it then treats the
> anomalous data and phases correctly is anyone's guess!
>
> The question is really whether it's likely ever to be _necessary_ to
> invert the hand; this will depend on the reciprocal space asymmetric
> unit chosen by the processing program. One could imagine a situation
> where the a.u. chosen by one processing program was on a different
> hand from the a.u. required by another. In such a situation you would
> have no choice but to invert the hand of the indices, though I suspect
> you would be better off doing it with CAD which will do it reliably,
> rather than reindex which may not (judging by the comments in the
> reindex code!). Whether such a situation ever occurs in practice, I
> don't know, maybe not.
>
> Cheers
>
> -- Ian
>
> On 29 May 2012 09:57, Graeme Winter <
[log in to unmask]> wrote:
>> Hello Qixu Cai,
>>
>> What you want is a reindexing operator which permutes the axes rather
>> than one which changes the sign of an axis. The easiest way to do this
>> is with pointless:
>>
>> pointless hklin input.mtz hklref reference.mtz hklout output.mtz
>>
>> and let pointless figure out the right operation to use. You may find
>> the following helpful:
>>
>>
http://www.ccp4.ac.uk/html/reindexing.html
>>
>> Best wishes,
>>
>> Graeme
>>
>> On 29 May 2012 09:48, Qixu Cai <
[log in to unmask]> wrote:
>>> Dear all,
>>>
>>> I have a dataset at P321 space group. And I want to reindex from (h,k,l) to
>>> (k,h,l) or (h,k,-l), because I want to merge this dataset to the native
>>> dataset.
>>> At first, I used the "reindex" program in CCP4i, and got an error: (either
>>> for (k,h,l) or (h,k,-l))
>>>
>>> ================================================
>>> Data line--- reindex HKL h, k, -l
>>> Data line--- end
>>>
>>> $TEXT:Warning: $$ comment $$
>>> WARNING: !!!! Reindexing matrix INVERTS hand !!!!
>>> $$
>>> REINDEX: !!!! You are NOT allowed to do this - Changing all signs in
>>> reindexing matrix
>>> Times: User: 0.0s System: 0.0s Elapsed: 0:00
>>> =================================================
>>>
>>> Could you please tell me the reason?
>>>
>>> At last, I converted the mtz file to CNS format, and write a script to
>>> exchange the h and k, and converted to mtz file.
>>> When I tried to use "cad" to merge this dataset to the native dataset, if I
>>> chose "Automatically check and enforce consistent indexing between different
>>> files",
>>> the index would be changed back to the original index. Why?
>>>
>>> Thank you very much for your attention.
>>>
>>> Best wishes,
>>>
>>> Qixu Cai
