[NeXus-tech] axes for multidimensional data

[Tobias Richter]

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.

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

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