[NeXus-tech] axes for multidimensional data

[Mark Koennecke]

Tobias,

Tobias Richter wrote:
> Hi Mark,
>
> On Tue, 2011-02-22 at 08:46 +0100, Mark Koennecke wrote:
>   
>> I am a little confused: up to now we had discussed this problem in the 
>> context of a scan in 2D or more. Not as
>> a general thing.
>>     
>
> As I wrote the @drive idea is an aside that might be useful, but I'd
> want it to be left out for now. Otherwise the problem is general only in
> that it applies to scans in nD with n>1.
>
>   
>> Then in the context of scans in 2D the problem has come up at PSI too. I 
>> will add another two ideas towards a solution
>> to the mess. The first is to use an additional data attribute which 
>> describes what has been meant:
>>
>> data:NXdata
>>      data[nx*ny]
>>          @signal=1
>>          @scan_intent=nx:ny
>>       x[nx*ny]
>>          @axis=1
>>          @primary=1
>>      y[nx*ny]
>>          @axis=1
>>     
>
> This (and Ben's suggestion) suffers from not passing the slicing test.
> For our users the main selling point of hdf5 is efficient storage of
> multi dimensional data. Here the view is almost the more dimensions the
> better - leave all the off-by-one errors in dealing with the arrays to
> the well tested file backend. This is important for user written
> analysis scripts.
>
>   
So, this is very important for some. This is good to know!

Let me add yet another suggestion:

data:NXdata
     data[nx*ny,512,512]
         @signal=1
         @scan_intent=0:1
      x[nx*ny]
         @axis=1
         @primary=1
     y[nx*ny]
         @axis=1

With this I try to make clear that I scanned the first and second axis 
and that axis data sets may
be multidimensional. Minimal change, fits the bill?

Mark

> But even if we will not find an agreement here, as long as it is legal
> to write data the way we prefer here, there should be a solution that
> solves our axis problem as well.
>
> Regards,
> Tobias
>
>