[Nexus] Correct way to specify multiple signals

[Jacob.Filik at Diamond.ac.uk]

Ah yes of course, I'm not sure we write that, we should.

(But it is one of the annoying attributes on the dataset, rather than the group, so you can only add it if you have control of what writes the HDF5 file, for externally linked data anyway).

Thanks.

Jake

-----Original Message-----
From: NeXus [mailto:nexus-bounces at shadow.nd.rl.ac.uk] On Behalf Of V. Armando Solé
Sent: 11 January 2018 13:16
To: nexus at nexusformat.org
Subject: Re: [Nexus] Correct way to specify multiple signals

On 11/01/2018 14:09, Jacob.Filik at Diamond.ac.uk wrote:

> This is really fun to try and do if energy can be the fast axis (for a dispersive detector) or the slow axes (for a monochromator scan) of the dataset.

The order of axes in NXdata should solve that.

Besides that, in the 2010 NIAC meeting it was decided to be able to associate an attribute"interpretation" to datasets with possible values "scalar", "spectrum", "image" precisely to know how to deal with multidimensional datasets assuming C order.

A 1000 x 2000 x 4000 dataset with attribute interpretation set to image would correspond to 1000 images of 2000 rows and 4000 columns.
A 1000 x 2000 x 4000 dataset with attribute interpretation set to spectrum would correspond to 1000 x 2000 spectra of 4000 channels.

At the ESRF we are using that since long ago and it is used to reduce user interaction and to present default views for individual datasets not selected via an NXdata group.

Armando

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