[Nexus] proposed additions to NXdata for non-linear scaling - to aid cbf interoperability

[jonathan.sloan at diamond.ac.uk]

Hi,

I've looked at muParser in a bit more detail now, it appears that while it isn't a completely general solution with full support for tensor operations (like MATLAB, for example) it does have a 'bulk' mode which would allow expressions to be defined per-frame and data to be extracted with per-frame scaling factors and even per-frame expressions. Limiting expressions to applying a uniform expression to an entire frame will still allow it to cover everything that the cbf-nexus conversions might use.

This would mean that (in the case of rank-3 data) 'NXforumla' could contain a rank-1 tensor of expressions, which would be passed a set of rank-1 parameters. The actual values of the data could be extracted by calculating 'value[j,k] = f(data[i,j,k],var[i]...)' for each frame 'i' of dimensions 'j,k'. Higher dimensional data could be converted by extending this to 'value[k,l] = f(data[i,j,k,l],var[i,j]...)' for each frame 'i,j' of dimensions 'k,l', and so on for higher dimensions. I think it should largely be a matter of plumbing to implement this, rather than adding any functionality which doesn't currently exist.

Since everything required should already be implemented in the muParser library, could we start using this when converting cbf data and refine the implementation later on once an 'NXforumla' class definition has been standardised?

Thanks.

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